TPIC44H01DA datasheet(20/28 Pages) TI

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TPIC44H01

4-CHANNEL SERIAL AND PARALLEL HIGH-SIDE PRE-FET DRIVER

SLIS088 – SEPTEMBER 1998

POST OFFICE BOX 655303

• DALLAS, TEXAS 75265

PRINCIPLES OF OPERATION

external over-current threshold generation

The TPIC44H01 device provides several means for setting V(OVDS), the threshold voltage used to detect

over-current. Figure 13 shows operation of the V(OVDS) generation circuitry. Any voltage appearing at the

MUXOUT node (see Figure 13) will be forced across R1A, setting up a current equal to V(MUXOUT)/R1A. This

current is passed through R1B, a resistor matched to R1A, thereby generating an IR drop, V(OVDS), down from

V(PWR), which is identical to V(MUXOUT). The user can select either an internally generated ~1.25-V band-gap

reference or can provide an external reference voltage using the V(COMPx) pin to control V(OV). The internal

reference is selected by connecting the V(COMPx) pin to VCC. This forces a comparator with a threshold of VCC

– V(F) to a state where it controls the analog AMUX block to connect MUXOUT to internal Vref.

A user adjustable V(OVDS) threshold can be set by supplying a voltage to the V(COMPx) pin in the range of 0.1

to 2.5 V. With V(COMPx) voltage in this range, the comparator controlling AMUX is in the state where V(COMPx)

voltage is connected to MUXOUT. Proper layout techniques should be used in the grounding network for the

V(COMP) circuit on the TPIC44H01. Ground for the pre-driver and V(COMPx) network should be connected to a

Kelvin ground, if available. Otherwise, there should be a single point contact back to PGND of the FET array.

Improper grounding techniques may result in inaccurate fault detection.

Comp

AMUX

Op-Amp

Comp

VIO = ± 5 mV

VCC

R1B

R1A

Buffer

R1B/R1A Matching

± 5%

VIO = ± 10 mV

OVDS

Detection

MUXOUT

Internal

Vref(Vbg)

VCC –V(F)

Switched by

Serial Input

Bit or by

Parallel Input

Shared by Channels

1 and 2 or 3 and 4

VCC

V(PWR)

SRCx

V(PK_x)

V(COMPx)

VCC

V(OVDS)

NOTES: A. V(COMPx) should have at least 100 pF to ground to assure stability of the V(COMPx) amplifier.

B. Equation for dynamic fault threshold voltage at V(COMP):

(COMPx)

(t)

+ V

(PK_x)

e– t RC

) V

(COMPx)

(0)

Where V(COMPx)(t) is the voltage at V(COMPx) at time t, V(PK_x) is the voltage at V(PK_x) set by the R2 and R3 resistor

divider, C is the value of C1, R is the parallel combination of R4 and R5, and V(COMPx)(0) is the voltage set up by the R4

and R5 resistor divider.

(1)

Figure 13. Over-Current Fault Threshold Generation

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