33926 datasheet(13/25 Pages) FREESCALE

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Analog Integrated Circuit Device Data

Freescale Semiconductor

33926

FUNCTIONAL DESCRIPTION

FUNCTIONAL PIN DESCRIPTION

device circuitry is fully operational and the supply

IPWR(STANDBY) current is reduced to a few mA. Refer to Table

3, Static Electrical Characteristics, page 7.

H-BRIDGE OUTPUT (OUT1, OUT2)

These pins are the outputs of the H-Bridge with integrated

freewheeling diodes. The bridge output is controlled using

the IN1, IN2, D1, and D2 inputs. The outputs have PWM

current limiting above the ILIM threshold. The outputs also

have thermal shutdown (tri-state latch-OFF) with hysteresis

as well as short-circuit latch-OFF protection.

A disable timer (time tB) is incorporated to distinguish

between load currents that are higher than the ILIM threshold

and short-circuit currents. This timer is activated at each

output transition.

CHARGE PUMP CAPACITOR (CCP)

This pin is the charge pump output pin and connection for

the external charge pump reservoir capacitor. The allowable

value is from 30 nF to 100 nF. This capacitor must be

connected from the CCP pin to the VPWR pin. The device

cannot operate properly without the external reservoir

capacitor.

ENABLE INPUT (EN)

The EN pin is used to place the device in a Sleep mode so

as to consume very low currents. When the EN pin voltage is

a logic LOW state, the device is in Sleep mode. The device is

enabled and fully operational when the EN pin voltage is in

logic HIGH. An internal pulldown 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 input becomes disconnected.

FEEDBACK (FB)

The 33926 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 <RFB <300 Ω.

If PWM-ing is implemented using the disable pin inputs

(either D1 or D2), a small filter capacitor (~1.0 µF) may be

required in parallel with the RFB resistor to ground for spike

suppression.

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