JPH06295989A - Mos type semiconductor device - Google Patents

Abstract

PURPOSE:To avoid the increase of the number of elements and the complication of process. CONSTITUTION:The gate of a MOSFET 1 to protect a device from an excess current is divided into a gate 7 and a gate 8, and the voltage of a drain terminal 4 is detected by a resistor circuit 6 arranged between a drain and a source. MOSFET's 9, 10 which can turn off isolated MOSFET's M1, M2 in order according to the increase of the detected voltage are arranged.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a MOS type semiconductor device having a built-in overcurrent protection function.

[0002]

2. Description of the Related Art A conventional MOS semiconductor device will be described with reference to FIG. FIG. 3 is a circuit configuration diagram of a conventional lateral MOSFET having a built-in overcurrent protection function. This MOS
The current detection portion of the semiconductor device has an MO
A current detection MOSFET 12 (hereinafter, sense MOSFET) having a gate width having a constant ratio to the gate width of the detection MOSFET M3 in parallel with the SFET (hereinafter, detection MOSFET) M3, and a resistor for detecting a current flowing through the sense MOSFET 12. It is composed of R6 (hereinafter, sense resistor).

Further, the circuit portion is a reference voltage generating circuit 1.
3, the comparator 14 that compares the voltage generated in the sense resistor R6 with the reference voltage,
It is composed of an N-OFF MOSFET 15. When a current flows through the detected MOSFET M3, a current having a constant ratio is supplied to the sense MOSFET 12 and the sense resistor R.
6, and a voltage is generated in the sense resistor R6. The voltage generated in the sense resistor R6 is compared with the reference voltage of the reference voltage generation circuit 13 in the comparator 14, and if an overcurrent flows and becomes larger than the reference voltage, a signal is output from the comparator 14. This signal causes the next stage MOSFET 15
Is turned on, the gate voltage of the detected MOSFET M3 is lowered below the threshold voltage, and the detected MOSFET M3 is turned off.

[0004]

In the conventional MOS type semiconductor device configured as described above, the reference voltage generating circuit 13 and the comparator 14 are used to obtain an accurate sense ratio, and the overcurrent protection function is provided. It was necessary to increase the number of elements and complicate the process in order to incorporate the device.

An object of the present invention is to construct a MOS type semiconductor device having a built-in overcurrent protection function without complicating the process and increasing the number of constituent elements.

[0006]

SUMMARY OF THE INVENTION A MOS semiconductor device of the present invention separates a gate electrode of a MOSFET to be detected into several parts, and detects a drain voltage.
A drain voltage dividing resistance circuit is provided between the sources.
Further, an input resistance is provided for all the separated gates, and a plurality of driving elements for controlling the gate voltage to be equal to or lower than the threshold voltage by being controlled by the divided drain voltage are provided between the gate and the source. . Further, the resistance circuit for controlling the drive elements has the same number of outputs as the divided gate electrodes, all outputs have different division ratios, and a plurality of drive elements operate sequentially as the drain voltage increases. .

[0007]

According to the present invention, as the drain voltage rises, the potential of the divided gate electrode becomes lower than the threshold value, and the MOSFET driven by the gate electrode is turned off. Therefore, the gate width is shortened in the entire MOSFET to be detected, and the flowing current value is reduced.

As described above, a MOS type semiconductor device having a built-in overcurrent protection function can be constructed only by adding a resistor and a driving element as constituent elements.

[0009]

1 is an internal equivalent circuit diagram of an embodiment of a MOS type semiconductor device of the present invention, and FIG. 2 is a plan view of a polysilicon gate of a MOSFET to be detected. 1 and 2
, 1 is a detected MOSFET, 2 is a polysilicon gate, 7 is a left side gate divided into left and right (FIG. 2 upper),
Reference numeral 8 denotes a gate on the right side (in FIG. 2), M1 denotes a MOSFET driven by the gate 7, M2 denotes a MOSFET driven by the gate 8, and 6 denotes a resistance circuit for dividing the drain voltage. The detected MOSFET 1 is composed of M1 and M2.

As shown in FIG. 2, the detected MOSFET 1
The gate polysilicon 2 is divided into two (here, the division ratio of the gate width is 1: 1), and the electrode 3 is provided on each of them. In addition, as shown in FIG.
A resistor circuit 6 is provided between the source terminal 5 and the source terminal 5 and has two outputs having different division ratios. Further, the two divided gates 7 and 8 are provided with input resistors R4 and R5, and an N-channel MOS is provided between each gate and source.
FETs 9 and 10 are provided.

The N-channel MOSFETs 9 and 10 are driven by the output of the resistance circuit 6 and have a function of lowering the voltage of the gates 7 and 8 below the threshold voltage when the voltage of the drain terminal 4 exceeds a certain value. (Here, MOSFE
T9 operates at a low drain voltage. ) Also, the resistance R4
In the ON state, the potential of the gate 8 is maintained at the voltage value of the gate terminal 11 even when the MOSFET 9 operates to lower the potential of the gate 7 and the MOSFET M1 is turned off. Further, the resistor R5 prevents overcurrent from flowing through the MOSFET 10.

In an actual use state, if an overcurrent tries to flow between the drain and source of the MOSFET 1 to be detected due to a short-circuited load in the on state, the voltage of the drain terminal 4 rises. When the drain voltage rises, a voltage given by the division ratio of the resistance R1 and the resistance R2 + R3 of the resistance circuit 6 is applied to the gate terminal of the MOSFET 9, and when the threshold voltage is exceeded, the MOSFET 9 turns on and the gate 7
When the voltage of the
The FET M1 is turned off. As a result, the gate width is 1/2
And the drain-source current decreases.

When a current further tries to flow, the drain voltage further rises, and when the voltage given by the division ratio of the resistors R1 + R2 and the resistor R3 exceeds the threshold voltage of the MOSFET 10, the MOSFET 10 is turned on and the MOSF is turned on.
ETM2 is turned off. As a result, the detected MOSFET
1 is completely turned off, and the drain-source current does not flow. As described above, the detected MOSFET 1 can be protected from overcurrent.

On the other hand, the structure of the elements constituting this device is as follows: The detected MOSFET 1 is an N-channel vertical double-diffused MOSFET in which cells are arranged in a mesh, and the resistors are ion-implanted polysilicon resistors and MOSF.
ETs 9 and 10 use N-channel lateral MOSFETs formed inside P-type wells. Therefore, a MOSFET having an overcurrent protection function can be constructed only by adding a step of forming a P-type well for forming an N-channel lateral MOSFET to the process of a single N-channel vertical double diffusion MOSFET. it can.

As described above, according to this MOS type semiconductor device, the gate 2 of the MOSFET 1 to be detected is separated into two parts, the drain voltage is detected by the resistance circuit 6, and the drain voltage is separated into two parts as the drain voltage rises. By adopting a circuit configuration in which the MOSFETs can be sequentially turned off, the number of elements can be reduced to 5 in a single N-channel vertical double diffusion MOSFET.
With regard to the process, only by adding an element, by adding a step of forming a P-type well for forming an N-channel lateral MOSFET, an M-type with an overcurrent protection function is built in.
An OSFET can be constructed.

[0016]

According to the present invention, the MOSFET to be detected is
By dividing the gate of the device into several parts, detecting the drain voltage by the drain voltage dividing resistance circuit provided between the drain and source, and providing a drive circuit that can turn off the separated MOSFETs in sequence according to the rise. Therefore, it is possible to configure a MOS semiconductor device having a built-in overcurrent protection function without increasing the number of elements and complicating the process.

[Brief description of drawings]

FIG. 1 is an internal circuit diagram of an embodiment of a MOS semiconductor device of the present invention.

2 is a detected MO of the MOS semiconductor device shown in FIG.
It is a top view of the polysilicon gate of SFET.

FIG. 3 is an internal circuit configuration diagram of a conventional MOS semiconductor device.

[Explanation of symbols]

1 Detected MOSFET 2 Polysilicon Gate 3 Gate Electrode 4 Drain Terminal 5 Source Terminal 6 Drain Voltage Dividing Resistor Circuit 9 MOSFET 10 MOSFET 11 Gate Terminal M1 Divided Left Side Gate (Upper FIG. 2) MOSFET M2 Divided Driven to the right side gate (on the upper side of FIG. 2) R1 resistor for dividing voltage between drain and source R2 resistor for dividing voltage between drain and source R3 resistor for dividing voltage between drain and source

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁵ Identification code Office reference number FI technical display location 9054-4M H01L 29/78 301 K

Claims (2)

[Claims] 1. A MOSFET having a plurality of gates and a plurality of gate electrodes formed therein, a drain voltage dividing resistance circuit connected between the drain and source of the MOSFET, and a gate electrode and a source of the MOSFET. And a plurality of driving elements which are respectively connected between them and are controlled by the drain voltage divided by the drain voltage dividing resistance circuit to reduce the gate voltage of each gate of the MOSFET to a threshold voltage or less. Type semiconductor device. 2. The MOS type semiconductor device according to claim 1, wherein the dividing ratios of the drain voltage dividing resistance circuits are all different values, and a plurality of driving elements are sequentially operated as the drain voltage increases.