NCV7708

http://onsemi.com

10

DETAILED OPERATING DESCRIPTION

General

The NCV7708 Double Hex Driver provides drive

capability for 3 independent H−Bridge configurations, or 6

High Side configurations with 6 Low Side configurations, or

any combination of arrangements. Each output drive is

characterized for a 500 mA load and has a typical 1.0 A surge

capability (at 12 V). Strict adherence to integrated circuit die

temperature is necessary. Maximum die temperature is

150

°C. This may limit the number of drivers enabled at one

time. Output drive control and fault reporting is handled via

the SPI (Serial Peripheral Interface) port.

An Enable function (EN) provides a low quiescent sleep

current mode when the device is not being utilized. No data

is stored when the device is in sleep mode. A pull down

current source is provided on the EN input to ensure the

device is off if the input signal is lost. Pull down current

sources are also provided on the SI and SCLK inputs. A pull

up current source is provided for the CSB input for the same

reason. A loss of signal pulls the CSB input high to stop any

spurious signals into the SPI port.

Power Up/Down Control

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

respective output drivers (VS1 powers OUTH1, OUTH2,

OUTH3, all 6 charge pumps and all 6 low side pre−drivers.

VS2 powers OUTH4, OUTH5, and OUTH6). All drivers are

initialized in the off (high impedance) condition, and will

The voltage on VS1 and VS2 should be operated at the same

potential.

A built−in hysteresis on the under voltage threshold is

included to prevent an unknown region on the power pins.

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 from the initial

under voltage threshold, or if shut down by either a SPI

command or a fault condition.

Internal power−up circuitry on the logic supply pin

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

power is applied. Exceeding the under voltage lockout

SPI port for turn on control. Logic information remains

intact over the entire VS1 and VS2 voltage range.

Current Limitation

Input bit 13 (OCD) controls the action of driver shutoff

during current limit. With a 0 for bit 13, there is no driver

shutoff, and the drivers current limit at 3 A. With a 1 for input

bit 13, the output drivers shut off when the shutdown

threshold current is passed. Devices can be turned back on

via the SPI port. Note: high currents could cause a high rise

in die temperature. Devices will not turn on if the die

temperature exceeds the thermal shutdown temperature.

Over Current Detection Shut Down

OCD Input

Bit 13

OUTx OCD

Condition

Output Data Bit 13 Over

Load Detect (OLD) Status

OUTx Status

Current Limit

of all Drivers

0

0

0

Unchanged

3 A

0

1

1 (Need SRR to reset)

Unchanged

3 A

1

0

0

Unchanged

3 A

1

1

1 (Need SRR to reset)

OUTx Latches Off (Need SRR to reset)

3 A

Under load Detection

The under−load detection is accomplished by monitoring

the current from each output driver. A minimum load current

(this is the maximum open circuit detection threshold) is

required when the drivers are turned on. If the under−load

circuit detection threshold has been crossed for more than

the under−load delay time, the bit indicator (output bit #14)

for open circuit will be set to a 1. In addition, the offending

driver will be turned off only if input bit 14 (ULD) is set to

1 (true).

Under Load Detection Shut Down

ULD Input

Bit 14

OUTx ULD

Condition

Output Data Bit 14 Under

Load Detect (ULD) 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)

OUTx Latches Off (Need SRR to reset)