TWI484313B - Reference voltage generating circuit and voltage adjusting device having negative charge protection mechanism of the same - Google Patents

Description

Reference voltage generating circuit and voltage adjusting device with negative charge protection mechanism

The present invention relates to a circuit protection technique, and more particularly to a reference voltage generating circuit and a voltage regulating device having a negative charge protection mechanism.

The reference voltage generation circuit converts the system voltage into a reference voltage that a module can receive and operate on. Therefore, how to generate a stable reference voltage so that each circuit module performs normal operation after receiving the reference voltage is an important issue for whether the entire system can perform normally.

In the reference voltage generating circuit, some of the end points may be used for fine-tuning or measuring the voltage, and a connection pad is required. The connection pads are prone to the effect of antenna accumulation and introduce negative charges into the circuit. When negative charges accumulate in some components, it is possible to The characteristics cause an impact that further prevents the circuit from functioning properly.

Therefore, how to design a new reference voltage generating circuit and its voltage regulating device with a negative charge protection mechanism to solve the above problems is an urgent problem to be solved in the industry.

Therefore, an aspect of the present invention provides a voltage adjusting device having a negative charge protection mechanism, comprising: a voltage adjusting module and a rectifying element having reverse diode characteristics. The voltage adjustment module is coupled to the reference voltage output end, and the reference voltage output end is coupled to the back end circuit, wherein the voltage adjustment module has a plurality of control input ends, and the resistance value of the voltage adjustment module is changed when the control voltage is received.进行Adjust the reference voltage output from the reference voltage output. The rectifying component is coupled to the reference voltage output end and the ground end, and when the input negative charge is transmitted from the control input end of the voltage adjusting module to the reference voltage output end, the input negative electric charge is introduced to the ground end.

Another aspect of the present invention provides a voltage regulating device having a negative charge protection mechanism, including: a voltage adjustment module and a charge buffering component. The voltage adjustment module is coupled to the reference voltage output end, and the reference voltage output end is coupled to the back end circuit, wherein the voltage adjustment module has a plurality of control input ends, and the resistance value of the voltage adjustment module is changed when the control voltage is received.进行Adjust the reference voltage output from the reference voltage output. The first end of the charge buffering component is coupled to the reference voltage output end, and the second end of the charge buffering component is coupled to the back end The time delays the input of the negative charge to the back-end circuit when the input negative charge is transferred from the control input to the reference voltage output.

Still another aspect of the present invention provides a reference voltage generating circuit including: a reference voltage generating device and a voltage adjusting device. The reference voltage generating device generates a reference voltage at the reference voltage output according to the system voltage, wherein the reference voltage output terminal is coupled to the back end circuit. The voltage adjusting device comprises: a voltage adjusting module and a rectifying element having a reverse diode characteristic. The voltage adjustment module is coupled to the reference voltage output end, wherein the voltage adjustment module has a plurality of control input terminals, and the resistance value of the voltage adjustment module is changed when the control voltage is received, and the reference voltage outputted by the reference voltage output terminal is adjusted. . The rectifying component is coupled to the reference voltage output end and the ground end, and when the input negative charge is transmitted from the control input end of the voltage adjusting module to the reference voltage output end, the input negative electric charge is introduced to the ground end.

Still another aspect of the present invention provides a reference voltage generating circuit including: a reference voltage generating device and a voltage adjusting device. The reference voltage generating device generates a reference voltage at the reference voltage output according to the system voltage, wherein the reference voltage output terminal is coupled to the back end circuit. The voltage adjusting device comprises: a voltage adjusting module and a charge buffering component. The voltage adjustment module is coupled to the reference voltage output end, wherein the voltage adjustment module has a plurality of control input terminals, and the resistance value of the voltage adjustment module is changed when the control voltage is received, and the reference voltage outputted by the reference voltage output terminal is adjusted. . The first end of the charge buffering component is coupled to the reference voltage output end, and the second end of the charge buffering component is coupled to The back-end circuit delays the time that the input negative charge is transferred to the back-end circuit when the input negative charge is transferred from the control input to the reference voltage output.

Yet another aspect of the present invention is to provide an integrated circuit comprising: at least one internal measurement pad and at least one rectifying element having reversed diode characteristics. The internal measuring pad can be used to measure the potential of the internal measuring point by the probe, and the internal measuring pad is coupled to the back end circuit; the rectifying element with the reverse diode characteristic is coupled to the internal measuring pad And a ground terminal for introducing an input negative charge of the internal measurement pad to the ground.

The invention has the advantages that the negative charge generated by the voltage adjustment module is led to the ground terminal or delayed by the reference voltage output terminal by the setting of the rectifying component and/or the charge buffering component with the reverse diode characteristic. The time to enter the back-end circuit avoids the accumulation of negative charges on the back-end circuit and easily achieves the above purpose.

1‧‧‧reference voltage generation circuit

10‧‧‧reference voltage generating device

12‧‧‧Voltage adjustment device

120‧‧‧Voltage adjustment module

122‧‧‧Rectifying components

14‧‧‧ Back-end circuit

20a, 20b, 20c‧‧‧ adjustment unit

200‧‧‧Adjust the resistance

202‧‧‧Fuse

204‧‧‧Control input pads

30‧‧‧Controlled rectifier

32‧‧‧Gold oxygen half diode

34‧‧‧Double-polar junction diode

4‧‧‧reference voltage generation circuit

40‧‧‧reference voltage generating device

42‧‧‧Voltage adjustment device

420‧‧‧Voltage adjustment module

422‧‧‧Charge buffer components

44‧‧‧ Back-end circuit

5‧‧‧reference voltage generation circuit

50‧‧‧reference voltage generating device

52‧‧‧Voltage adjustment device

520‧‧‧Voltage adjustment module

522‧‧‧Rectifying components

524‧‧‧Charge buffer components

54‧‧‧Back-end circuit

6‧‧‧reference voltage generation circuit

60‧‧‧Measurement pads

62‧‧‧Rectifying components

7‧‧‧ Back-end circuit

1 is a circuit diagram of a reference voltage generating circuit according to an embodiment of the present invention; FIG. 2 is a circuit diagram of a voltage adjusting module according to an embodiment of the present invention; and FIGS. 3A to 3C are respectively an embodiment of the present invention; In the example, the display of the rectifier, the gold-oxygen semiconductor, and the bipolar junction diode 4 is a circuit diagram of a reference voltage generating circuit according to an embodiment of the present invention; FIG. 5 is a circuit diagram of a reference voltage generating circuit according to an embodiment of the present invention; and FIG. 6 is a reference of an embodiment of the present invention; A circuit diagram of a voltage generating circuit; and FIGS. 7A and 7B are graphs of yield statistics of wafers on a wafer before and after application of an embodiment of the present invention.

Please refer to Figure 1. 1 is a circuit diagram of a reference voltage generating circuit 1 according to an embodiment of the present invention. The reference voltage generating circuit 1 includes a reference voltage generating device 10 and a voltage adjusting device 12.

The reference voltage generating device 10 generates a reference voltage Vref at the reference voltage output terminal O according to the system voltage Vdd, wherein the reference voltage output terminal O is coupled to the back circuit 14 (subsequent circuitry). In this embodiment, the reference voltage generating device 10 can be a bandgap reference voltage generating circuit as shown in FIG. 1. However, in other embodiments, the reference voltage generating device 10 can also be implemented by other circuits, and is not limited to the example of FIG. 1.

The voltage adjustment device 12 includes a voltage adjustment module 120 and a rectifying element 122 having reversed diode characteristics. The voltage adjustment module 120 is coupled to the reference voltage output terminal O, wherein the voltage adjustment module 120 There are complex control inputs, such as control inputs P1, P2, P3 and P4 shown in FIG. When the control input terminals P1 - P4 respectively receive a control voltage (Vtrim; trimming voltage) (not shown), the resistance value of the voltage adjustment module 120 can be changed to output the reference voltage Vref to the reference voltage output terminal O. The values are adjusted and will be explained in detail later.

Please refer to Figure 2. FIG. 2 is a circuit diagram of a voltage adjustment module 120 according to an embodiment of the invention. In the present embodiment, the voltage adjustment module 120 includes a plurality of adjustment units 20a, 20b, and 20c connected in series, and the adjustment units 20a, 20b, and 20c each include a parallel adjustment resistor 200 and a fuse 202. Two ends of each of the adjusting units 20a, 20b and 20c respectively correspond to two of the control inputs. For example, both ends of the adjusting unit 20a correspond to the control input terminals P1 and P2, and both ends of the adjusting unit 20b correspond to the control input terminals P2 and P3, and both ends of the adjusting unit 20c correspond to the control input terminals P3 and P4. In one embodiment, control inputs P1-P4 include control input pads 204, respectively. The control input pad 204 is not a bonding pad and is only for receiving a control voltage. That is, the control input pad 204 does not have a gold bond, and will not be exposed to the package structure after the package process is completed, and thus will not be coupled to other circuits.

Before the control voltage is received at both ends of each of the adjustment units 20a, 20b, and 20c, the adjustment resistor 200 is bypassed by the fuse 202, and thus will be in a short-circuited state. When adjusting units 20a, 20b and 20c After the two terminals receive a control voltage in sequence, the control voltage will blow the fuse 202 so that the resistor 200 can be adjusted. For example, one end (P1 end) of the adjusting unit 20a is first coupled to a control voltage, and the other end (P2 end) is grounded, and the fuse 202 of the adjusting unit 20a is blown. Next, one end (P2 end) of the adjusting unit 20b is coupled to the above control voltage, and the other end (P3 end) is grounded, and the fuse 202 of the adjusting unit 20b is blown. Finally, one end (P3 end) of the adjusting unit 20c is coupled to the above control voltage, and the other end (P4 end) is grounded, and the fuse 202 of the adjusting unit 20c is blown. Therefore, the resistance of the adjustment resistor 200 of the adjustment units 20a, 20b, and 20c will increase the reference voltage Vref of the reference voltage output terminal O. However, the fuses 202 in the adjustment units 20a, 20b, and 20c are not necessarily all in a blown state. In an embodiment, an adjustment unit that needs to blow the fuse 202 can be determined by a control unit (not shown), and the control voltage is sequentially supplied to both ends of the corresponding adjustment unit to blow the fuse 202. When the reference voltage generating device 10 causes an error due to component processing or other reasons, and the reference voltage Vref is inaccurate, it can be adjusted by the setting of the voltage adjusting module 120.

It should be noted that, in this embodiment, three adjustment units and four control input terminals are taken as an example. In other embodiments, the number of adjustment units and control input terminals may be adjusted according to circumstances. Moreover, the resistance of the adjustment resistors in each adjustment unit may be the same, or may be increased by a multiple of, for example, but not limited to, to achieve a more effective adjustment effect. In some embodiments, the circuit of the voltage adjustment module 120 is also Other design forms may be used, which are not limited by the description in the embodiment.

However, when performing the step of die sawing in the circuit process, the control input pad 204 has the characteristics of antenna aggregation, and it is easy to introduce a negative charge. Wafer cutting steps are usually cooled with pure water rinsing, but they do not carry away negative charges. Although in some technologies, ionized water of carbonated water is used in an attempt to carry away negative charges, its effectiveness is still limited. Moreover, the control input pads of the wafer are generally provided with no ESD protection components, and therefore there is no path to discharge the above negative charges. The negative charge of these inputs will be transferred to the reference voltage output terminal O via the voltage adjustment module 120 and further to the back end circuit 14. When a component of the back-end circuit 14, such as a transistor, receives a negative charge, it may accumulate at its gate, thereby causing its threshold voltage (Vt) to drop during operation, which will affect the normal operation of the circuit.

Therefore, as shown in FIG. 1, the rectifying component 122 having the reverse diode characteristic is coupled to the reference voltage output terminal O and the grounding terminal GND, and can input a negative charge from the control input terminal P1- of the voltage adjusting module 120. When P4 is transmitted to the reference voltage output terminal O, the input negative charge is introduced from the path A to the ground GND.

In the embodiment of Figure 1, the rectifying element 122 is a reverse diode. In the present embodiment, the reverse direction refers to the connection mode in which the anode (Anode) is connected to the ground GND and the cathode (Cathode) is connected to the reference voltage output terminal O. The voltage across the rectifying element 122 is the clamping voltage V _clamp .

Please refer to Figures 3A to 3C. 3A to 3C are respectively a controllable rectifier (SCR) 30, a MOS diode 32, and a bipolar junction diode (BJT) according to an embodiment of the invention. Schematic diagram of diode)34. The voltage controlled rectifier 30, the gold-oxygen semiconductor diode 32 and the bipolar junction diode 34 have the characteristics of a diode, so that after the appropriate connection mode, the reverse diode can also be used as a rectifier. Element 122. It should be noted that the 3B and 3C are exemplified by the N-type MOS diode 32 and the bipolar junction diode 34. In other embodiments, the P-type MOS can also be used. The diode and the bipolar junction diode are realized. In other embodiments, other components having diode characteristics can also be implemented to achieve the same effect as the rectifying element 122.

It should be noted that, in an embodiment, to ensure that a negative charge is introduced to the ground GND along the path A of FIG. 1, the clamp voltage V _{clamp of the} rectifying element 122 can be made larger than the control voltage V _trim . That is, the following formula must be satisfied: V _clamp >V _trim

In addition, the clamping voltage V _clamp described above cannot be greater than a gate breakdown voltage of the transistor of the back end circuit 14 to avoid affecting the operation of the back end circuit 14. Therefore, the voltage adjusting device 12 in the reference voltage generating circuit 1 of the present invention can introduce the negative electric charge generated by the control input pad due to the antenna gathering effect to the ground end by using the rectifying element having the reverse diode characteristic, thereby avoiding Accumulation in the back-end circuit causes the back-end circuit to not function properly.

Please refer to Figure 4. Fig. 4 is a circuit diagram of a reference voltage generating circuit 4 in accordance with an embodiment of the present invention. Similarly, the reference voltage generating circuit 4 includes a reference voltage generating device 40 and a voltage adjusting device 42. The components in the reference voltage generating circuit 4 are substantially the same as those in the reference voltage generating circuit 1 of Fig. 1, and therefore the description of the same portions will not be repeated. In the embodiment, the voltage adjusting device 42 further includes a charge buffering component 422 in addition to the voltage adjusting module 420.

The first end of the charge buffering component 422 is coupled to the reference voltage output terminal O, and the second end is coupled to the back end circuit 44. The input negative charge is transmitted from the control input terminal O along the path B to the reference voltage output terminal O and thereafter. The terminal circuit 44 delays the time at which the input negative charge is transferred to the back end circuit 44. In the present embodiment, the charge buffering element 422 is a resistor. Since the charge buffering element 422 is used to delay the time during which the input negative charge is transferred to the back end circuit 44, its resistance value only needs to be greater than the water resistance at the time of wafer cutting. In one embodiment, the charge buffer element has a resistance value of 3K ohms, and the series adjustment unit has a resistance value of 85K ohms. In other embodiments, other components that mitigate the transfer of negative charge to the back end circuitry 44 may also be employed.

Therefore, during the wafer cutting step, such as washing with ionized water of carbonated water, there will be enough time to carry the negative charge away, so as to avoid accumulation of negative charge in the back-end circuit and cause the back-end circuit. The effect of not working properly.

Please refer to Figure 5. Fig. 5 is a circuit diagram of a reference voltage generating circuit 5 in accordance with an embodiment of the present invention. Similarly, the reference voltage generating circuit 5 includes a reference voltage generating device 50 and a voltage adjusting device 52. The components in the reference voltage generating circuit 5 are substantially the same as those in the reference voltage generating circuit 1 of Fig. 1, and therefore the description of the same portions will not be repeated. In the present embodiment, the voltage adjusting device 52 includes a voltage rectifying module 520 and a rectifying element 522 and a charge buffering element 524 having reversed diode characteristics.

The first end of the charge buffering component 524 is coupled to the reference voltage output terminal O and the rectifier component 522 , and the second terminal is coupled to the back end circuit 54 . Therefore, with the arrangement of FIG. 5, the voltage adjusting device 52 can first introduce a negative charge to the ground GND by the rectifying element 522, and delay the time when the negative charge is transferred to the back end circuit 54 by the charge buffering element 524.

It should be noted that the above embodiment is an example in which a negative electric charge is input from a control input terminal of the voltage adjustment module in the voltage adjustment device. Please refer to Figure 6. Fig. 6 is a circuit diagram of a reference voltage generating circuit 6 in accordance with an embodiment of the present invention. The reference voltage generating circuit 6 can generate the reference voltage Vref to the back end circuit 7 at the reference voltage output terminal O. In the present embodiment, a probing pad 60 can be disposed at a measurement point N at the reference voltage generating circuit 6. The measuring pad 60 can be used to measure the potential of the measuring point N by a probe or other means. Similarly, at the step of wafer dicing, the measurement pad 60 has the characteristics of antenna aggregation, and it is easy to introduce a negative charge, which affects the operation of the elements in the reference voltage generating circuit 6. In general, the measurement pads inside the wafer are not provided with electrostatic protection components, and there is no path to discharge the above negative charges. Therefore, the effect of conducting the negative charge to the ground potential GND can also be achieved by the arrangement of the rectifying element 62 having the reverse diode characteristics. Referring to Figure 6, the rectifying element 62 is a reverse diode. In the present embodiment, the reverse direction refers to the connection mode in which the anode (Anode) is connected to the ground GND, and the cathode (Cathode) is connected to the measuring point N. The voltage across the rectifying element 62 is the clamping voltage V _clamp . In addition, the clamp voltage V _{clamp of} the rectifying element 6 described above cannot be greater than a gate breakdown voltage of the transistor in the reference voltage generating circuit 6 to avoid affecting the operation of the reference voltage generating circuit 6. Similarly, the charge buffering element 422 as shown in FIG. 4 can also be applied to achieve the effect of buffering charges into other components in the reference voltage generating circuit 6. In the above embodiment, the measurement pad is located in the reference voltage generating circuit, but the measuring pad of any one of the measuring points in the wafer (or the bit voltage generating circuit) may be disposed. Or a charge buffering element or a combination of the two to cause a negative charge in the circuit to be conducted to the ground potential GND, wherein the clamping voltage V _{clamp of} the rectifying element cannot be greater than a gate breakdown voltage of the transistor of the back end circuit to avoid Affect the operation of the back-end circuit.

7A and 7B are graphs showing yield statistics of wafers on a wafer before and after application of an embodiment (Fig. 4) of the present invention, respectively. The horizontal axis is the bandgap reference measured for each wafer on the wafer. The voltage range of the voltage, the vertical axis is the number of wafers at the corresponding measured voltage. We can observe that the wafer yield using the present invention is significantly improved (Fig. 7B), and the number of wafers falling within the specification of the final test (FT) is increased, and the wafers that do not meet the final test specifications of the mass production are relatively cut back.

The present disclosure has been disclosed in the above embodiments, but it is not intended to limit the disclosure, and any person skilled in the art can make various changes and refinements without departing from the spirit and scope of the disclosure. The scope of protection of the disclosure is subject to the definition of the scope of the patent application.

1‧‧‧reference voltage generation circuit

10‧‧‧reference voltage generating device

12‧‧‧Voltage adjustment device

120‧‧‧Voltage adjustment module

122‧‧‧Rectifying components

14‧‧‧ Back-end circuit

Claims (16)

A voltage adjustment device with a negative charge protection mechanism includes: a voltage adjustment module coupled to a reference voltage output terminal, wherein the reference voltage output terminal is coupled to a back end circuit, wherein the voltage adjustment module has a plurality of a control input, changing a resistance value of the voltage adjustment module when receiving a control voltage, adjusting a reference voltage of the output of the reference voltage output; and a rectifying component having a reverse diode characteristic, The input voltage is coupled to the reference voltage output terminal and a ground terminal. When an input negative charge is transmitted from the control input terminals of the voltage adjustment module to the reference voltage output terminal, the input negative charge is introduced to the ground terminal. The voltage adjusting device of claim 1, further comprising a charge buffering component, wherein the first end of the charge buffering component is coupled to the reference voltage output terminal and the rectifying component, and the second end of the charge buffering component is coupled Connected to the back-end circuit, delaying the input of the negative charge to the back-end circuit when the input negative charge is transferred from the control input to the reference voltage output. The voltage adjustment device of claim 1, wherein the voltage adjustment module comprises a plurality of adjustment units connected in series, and the adjustment units each comprise a parallel adjustment resistor and a fuse, wherein the two ends of each of the adjustment units Corresponding to two of these control inputs The two ends of each of the adjusting units bypass the adjusting resistor by the fuse before receiving the control voltage, and after receiving the control voltage, blow the fuse to enable the adjusting resistor. The voltage adjusting device of claim 1, wherein one of the rectifying elements has a clamping voltage greater than the control voltage. The voltage adjusting device of claim 3, wherein the control input terminals respectively comprise a control input pad, wherein the control input pad is not a bonding pad. A voltage adjustment device with a negative charge protection mechanism includes: a voltage adjustment module coupled to a reference voltage output terminal, wherein the reference voltage output terminal is coupled to a back end circuit, wherein the voltage adjustment module has a plurality of Controlling an input terminal, changing a resistance value of the voltage adjustment module when receiving a control voltage, adjusting a reference voltage of the output of the reference voltage output terminal; and a charge buffering component, the one of the charge buffering component One end of the charge buffering element is coupled to the reference voltage output end, and the second end of the charge buffering component is coupled to the back end circuit, and the input negative charge is delayed from the control input terminal to the reference voltage output terminal The time at which the input negative charge is transferred to the back end circuit. The voltage adjustment device of claim 6, wherein the voltage adjustment module comprises a plurality of adjustment units connected in series, and each of the adjustment units comprises a parallel adjustment resistor and a fuse, wherein the two ends of each of the adjustment units Corresponding to two of the control input terminals, both ends of each of the adjustment units bypass the adjustment resistor by the fuse before receiving the control voltage, and after the control voltage is received, the fuse is blown to enable the Adjust the resistance. The voltage adjusting device of claim 7, wherein the control input terminals respectively comprise a control input pad, wherein the control input pad is not a solder pad. A reference voltage generating circuit includes: a reference voltage generating device for generating a reference voltage at a reference voltage output terminal according to a system voltage, wherein the reference voltage output terminal is coupled to a back end circuit; and a voltage adjusting device The method includes: a voltage adjustment module coupled to the reference voltage output end, wherein the voltage adjustment module has a plurality of control input terminals, and changes a resistance value of the voltage adjustment module when receiving a control voltage, The reference voltage output terminal is adjusted by a reference voltage; and a rectifying component having a reverse diode characteristic coupled to the reference voltage output terminal and a ground terminal, adjacent to an input negative power When the control input terminals of the voltage adjustment module are transmitted to the reference voltage output terminal, the input negative charge is introduced to the ground terminal. The reference voltage generating circuit of claim 9, wherein the voltage adjusting device further comprises a charge buffering component, wherein the first end of the charge buffering component is coupled to the reference voltage output terminal and the rectifying component, the charge buffering component A second end is coupled to the back end circuit for delaying the time during which the input negative charge is transferred to the back end circuit when the input negative charge is transferred from the control input to the reference voltage output. The reference voltage generating circuit of claim 9, wherein the voltage adjusting module comprises a plurality of adjusting units connected in series, and each of the adjusting units comprises a parallel adjusting resistor and a fuse, wherein each of the adjusting units The terminal corresponds to two of the control input terminals, and the two ends of each of the adjusting units bypass the adjusting resistor by the fuse before receiving the control voltage, and after the receiving the control voltage, the fuse is blown to enable The adjustment resistor. The reference voltage generating circuit of claim 9, wherein one of the rectifying elements has a clamping voltage greater than the control voltage. The voltage adjusting device of claim 11, wherein the The control input terminals respectively comprise a control input pad, wherein the control input pad is not a solder pad. A reference voltage generating circuit includes: a reference voltage generating device for generating a reference voltage at a reference voltage output terminal according to a system voltage, wherein the reference voltage output terminal is coupled to a back end circuit; and a voltage adjusting device The method includes: a voltage adjustment module coupled to the reference voltage output end, wherein the voltage adjustment module has a plurality of control input terminals, and changes a resistance value of the voltage adjustment module when receiving a control voltage, The reference voltage output terminal is adjusted by one of the reference voltages; and a charge buffering component, the first end of the charge buffering component is coupled to the reference voltage output end, and the second end of the one of the charge buffering components is coupled to the The back end circuit delays the time during which the input negative charge is transferred to the back end circuit when the input negative charge is transferred from the control input to the reference voltage output. The reference voltage generating circuit of claim 14, wherein the voltage adjusting module comprises a plurality of adjusting units connected in series with each other, and the adjusting units each comprise a parallel adjusting resistor and a fuse, wherein each of the adjusting units The end corresponds to two of these controls At the input end, the two ends of each of the adjusting units bypass the adjusting resistor by the fuse before receiving the control voltage, and after receiving the control voltage, blow the fuse to enable the adjusting resistor. The reference voltage generating circuit of claim 15, wherein the control input terminals respectively comprise a control input pad, wherein the control input pad is not a solder pad.