NCV7728DPAR2G datasheet(20/27 Pages) ONSEMI

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NCV7728

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DEVICE PROTECTION, DIAGNOSTICS AND FAULT REPORTING

Power Up/Down Control

Each analog power pin (VS1 or VS2) powers their

respective output drivers. After a device has powered up and

the output drivers are allowed to turn on, the output drivers

will not turn off until the voltage on the supply pins is

reduced below the initial under voltage threshold, exceeds

the over voltage threshold or if shut down by either a SPI

command or a fault condition.

Internal power−up circuitry on the logic supply pin

supports a smooth turn on transition. VCC power up resets

the internal logic such that all output drivers will be off as

power is applied. All the internal counters, SI and SO along

with all the digital registers will be cleared on VCC POR.

Exceeding the under voltage lockout threshold on VCC

allows information to be input through the SPI port for turn

on control. Logic information remains intact over the entire

VS1 and VS2 voltage range.

Under Voltage Shutdown

An under voltage lockout circuit prevents the output

drivers from turning on unintentionally. This control is

provided by monitoring the voltages on the VS1, VS2 and

VCC pins. A built−in hysteresis on the under voltage

threshold is included to prevent an unknown region on the

power pins; VCC, VS1 and VS2. When the VCC goes below

the threshold, all outputs are turned off and the input and

output registers are cleared.

An under voltage condition on the VSx pins will result in

shutting off all the drivers and the status bit 14 (PSF) will be

set. The SPI port remains active during a VSx under−voltage

if proper VCC voltage is supplied. Also all driver states will

be maintained in the logic circuitry with the valid VCC

voltage. Once the input voltage VSx is above the under

voltage threshold level the drivers will return to

programmed operation and the PSF output register bit is

cleared.

Under−voltage timing diagram is provided in Figure 21.

Figure 21. Under−Voltage Timing Diagram

OUTx

Fault

OUTx

PSF

ALL

OUTx

Fault

³0x00

ALL

VSx

Vcc

OUTx

VSUV

VccUV

No Fault

PSF

Fault

0x00

OUTx VS

Fault

OUTx

Fault

OUTx GND

Status

Output

State

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