33931 datasheet(12/21 Pages) FREESCALE

12 / 21 page

Analog Integrated Circuit Device Data

Freescale Semiconductor

33931

FUNCTIONAL DESCRIPTION

FUNCTIONAL PIN DESCRIPTION

The device is enabled and fully operational when the EN pin

voltage is logic HIGH. An internal pull-down resistor

maintains the device in Sleep mode in the event EN is driven

through a high-impedance I/O or an unpowered

microcontroller, or the EN/D2 input becomes disconnected.

FEEDBACK (FB)

The 33931 has a feedback output (FB) for “real time”

monitoring of H-bridge high side output currents to facilitate

closed-loop operation for motor speed and torque control.

The FB pin provides current sensing feedback of the

H-bridge high side drivers. When running in the forward or

reverse direction, a ground-referenced 0.24% of load current

is output to this pin. Through the use of an external resistor to

ground, the proportional feedback current can be converted

to a proportional voltage equivalent and the controlling

microcontroller can “read” the current proportional voltage

with its analog-to-digital converter (ADC). This is intended to

provide the user with only first-order motor current feedback

for motor torque control. The resistance range for the linear

operation of the FB pin is 100

Ω < RFB <300 Ω.

If PWM-ing is implemented using the disable pin input

(only D1), a small filter capacitor (~1.0 µF) may be required

in parallel with the RFB resistor to ground for spike

suppression.

33931 Datasheet(PDF) 12 Page - Freescale Semiconductor, Inc