TPIC46L01, TPIC46L02, TPIC46L03

6-CHANNEL SERIAL AND PARALLEL LOW-SIDE PRE-FET DRIVER

SLIS055A – NOVEMBER 1996 - REVISED SEPTEMBER 1997

13

POST OFFICE BOX 655303

PRINCIPLES OF OPERATION

open load

The TPIC46L01, TPIC46L02, and TPIC46L03 monitor the drain of each power FET for open-circuit conditions

that may exist. The 60-

µA current source is provided to monitor open-load fault conditions. Open-load faults are

detected when the power FET is turned off. When load impedance is open or substantially high, then the 60-

µA

current source has adequate drive to pull the drain of T1 below the fault reference threshold on the detection

reporting of open-load fault conditions. The on-board deglitch timer starts running when the TPIC46L01,

TPIC46L02, and TPIC46L03 gate output to the power FET transitions to the off state. The timer provides a 60-

µs

deglitch time is only enabled for the first 60

µs after the FET has been turned off. After the deglitch delay time,

the drain is checked to verify that it is greater than the fault reference voltage. When it is less than the reference

voltage, a fault is flagged to the microcontroller through FLT that an open-load fault condition exists. The

microcontroller can then read the serial port on the TPIC46L01, TPIC46L02, and TPIC46L03 to isolate which

channel reported the fault condition. Fault bits 0–5 distinguish faults for each of the output channels. Figure 15

illustrates the operation of the open-load detection circuit. This feature provides useful information to the

microcontroller to isolate system failures and warn the operator that a problem exists. Examples of such

applications would be warning that a light bulb filament may be open, solenoid coils may be open, etc.

NORMAL

_

+

N-Channel

Load

VBAT

T1

External

TPIC46L01/L02/L03

1.25 V

Deglitch

FLT

Input From

TPIC46L01/L02/L03

60

µA

U1

t(STBFM)

Glitches

Input

DRAIN0–

DRAIN5

FLT

OPEN-LOAD

NORMAL

GATE0–

GATE5

Input

DRAIN0–

DRAIN5

FLT

GATE0–

GATE5

t(STBFM)

Figure 15