NCV7708

http://onsemi.com

11

Over Voltage Shutdown

Over voltage shutdown circuitry monitors the voltage on

the VS1 and VS2 pins. When the Over−voltage Threshold

voltage level has been breached on both or either one of the

VSx supply inputs, output bit 15 will be set and, if input bit

15 (OVLO) is set to 1, all outputs will turn off. Turn on/off

status is maintained in the logic circuitry. When proper input

voltage levels are re−established, the programmed outputs

will turn back on. Over−voltage shutdown can be disabled

by using the SPI input bit 15 (OVLO = 0).

Over Voltage Lock Out (OVLO) Shut Down

OVLO In-

put Bit 15

VSx OVLO

Condition

Output Data Bit 15 Power

Supply Fail (PSF) Status

OUTx Status

0

0

0

Unchanged

0

1

1 (Need SRR to reset)

Unchanged

1

0

0

Unchanged

1

1

1 (Need SRR to reset)

All Outputs Off (Remain off until VSx is out of OVLO)

Thermal Shutdown

Six independent thermal shutdown circuits are featured

(one common sensor for each HS and LS transistor pair).

Each sensor has two levels, one to give a Thermal Warning

(TW) and a higher one, Over Temperature, which will shut

the drivers off. When the part reaches the temperature point

of Thermal Warning, the output data bit 0 (TW) will be set

to a 1, and the outputs will remain on. With one or more

sensors detecting the over temperature level, all channels

will be turned off simultaneously. All outputs will return to

normal operation when the part thermally recovers

(Thermal toggling), because the over temperature shutdown

does not change the actual channel selection. The output

data bit 0, Thermal Warning, will latch and remain set, even

after cooling, and is reset by using a software command to

input bit 0 (SRR). Since thermal warning precedes a thermal

shutdown, software polling of this bit will allow for load

control and possible prevention of thermal shutdown

conditions.

Thermal

warning

information

can

be

retrieved

immediately without performing a complete SPI access

cycle. Figure 4 below displays how this is accomplished.

Bringing the CSB pin from a 1 to a 0 condition immediately

displays the information on the output data bit 0, thermal

warning, even in the absence of a SCLK signal. As the

temperature of the NCV7708 changes from a condition from

below the thermal warning threshold to above the thermal

warning threshold, the state of the SO pin changes and this

level is available immediately when the CSB goes to 0. A 0

on SO indicates there is no thermal warning, while a 1

indicates the IC is above the thermal warning threshold. This

warning bit is reset by using the input data bit 0, SRR.

Figure 4. Access to Temperature warning information shows the thermal information is available immediately

with activation of the CSB signal without having to toggle the SCLK line.

CSB

SCLK

SO

CSB

SCLK

SO

TWH

NTW

No Thermal Warning

Thermal Warning High

Tristate Level

Tristate Level