DRV8800

DRV8801

SLVS855D – JULY 2008 – REVISED APRIL 2010

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Charge Pump

The charge pump is used to generate a supply above VBB to drive the source-side DMOS gates. A 0.1-mF

ceramic monolithic capacitor should be connected between CP1 and CP2 for pumping purposes. A 0.1-mF

ceramic monolithic capacitor, CStorage, should be connected between VCP and VBB to act as a reservoir to run

the high-side DMOS devices. The VCP voltage level is internally monitored and, in the case of a fault condition,

the outputs of the device are disabled.

Shutdown

As a measure to protect the device, faults caused by very high junction temperatures or low voltage on VCP

disable the outputs of the device until the fault condition is removed. At power on, the UVLO circuit disables the

drivers.

Low-Power Mode

Control input nSLEEP is used to minimize power consumption when the DRV8800/DRV8801 is not in use. This

disables much of the internal circuitry, including the internal voltage rails and charge pump. nSLEEP is asserted

low. A logic high on this input pin results in normal operation. When switching from low to high, the user should

allow a 1-ms delay before applying PWM signals. This time is needed for the charge pump to stabilize.

•

MODE 1 (MODE on the DRV8800)

Input MODE 1 is used to toggle between fast-decay mode and slow-decay mode. A logic high puts the device

in slow-decay mode.

•

MODE 2 (DRV8801 only)

MODE 2 is used to select which set of drivers (high side versus low side) is used during the slow-decay

recirculation. MODE 2 is meaningful only when MODE 1 is asserted high. A logic high on MODE 2 has

current recirculation through the high-side drivers. A logic low has current recirculation through the low-side

drivers.

Braking

The braking function is implemented by driving the device in slow-decay mode (MODE 1 pin is high) and

deasserting the enable to low. Because it is possible to drive current in both directions through the DMOS

switches, this configuration effectively shorts out the motor-generated BEMF as long as the ENABLE chop mode

is asserted. The maximum current can be approximated by VBEMF/RL. Care should be taken to ensure that the

maximum ratings of the device are not exceeded in worse-case braking situations – high-speed and high-inertia

loads.

Diagnostic Output

The nFAULT pin signals a problem with the chip via an open-drain output. A motor fault, undervoltage condition,

power dissipation mode (i.e., nSLEEP is low). nFAULT stays asserted (nFAULT = L) until VBB reaches VBBNFR

to give the charge pump headroom to reach its undervoltage threshold. nFAULT is a status-only signal and does

not affect any device functionality. The H-bridge portion still operates normally down to VBB = 8 V with nFAULT

asserted.

Thermal Shutdown (TSD)

Two die-temperature monitors are integrated on the chip. As die temperature increases toward the maximum, a

thermal warning signal is triggered at 160°C. This fault drives the nFAULT low, but does not disable the

operation of the chip. If the die temperature increases further, to approximately 175°C, the full-bridge outputs are

disabled until the internal temperature falls below a hysteresis of 15°C.

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