33931 Datasheet, PDF (11/21 Pages) Freescale Semiconductor, Inc – 5.0 A Throttle Control H-bridge

FUNCTIONAL DESCRIPTION
INTRODUCTION
FUNCTIONAL DESCRIPTION
INTRODUCTION
Numerous protection and operational features (speed,
torque, direction, dynamic breaking, PWM control, and
closed-loop control) make the 33931 a very attractive, cost-
effective solution for controlling a broad range of small DC
motors. The 33931 outputs are capable of supporting peak
DC load currents of up to 5.0 A from a 28 V V_PWR source. An
internal charge pump and gate drive circuitry are provided
that can support external PWM frequencies up to 11 kHz.
The 33931 has an analog feedback (current mirror) output
pin (the FB pin) that provides a constant-current source
ratioed to the active high side MOSFETs’ current. This can be
used to provide “real time” monitoring of output current to
facilitate closed-loop operation for motor speed/torque
control, or for the detection of open load conditions.
Two independent inputs, IN1 and IN2, provide control of
the two totem-pole half-bridge outputs. Two independent
disable inputs, D1 and EN/D2, provide the means to force the
H-bridge outputs to a high-impedance state (all H-bridge
switches OFF). The EN/D2 pin also controls an enable
function that allows the IC to be placed in a power-conserving
Sleep mode.
The 33931 has output current limiting (via constant OFF-
time PWM current regulation), output short-circuit detection
with latch-OFF, and over-temperature detection with latch-
OFF. Once the device is latched-OFF due to a fault condition,
either of the Disable inputs (D1 or EN/D2), or V_PWR must be
“toggled” to clear the status flag.
Current limiting (Load Current Regulation) is
accomplished by a constant-OFF time PWM method using
current limit threshold triggering. The current limiting scheme
is unique in that it incorporates a junction temperature-
dependent current limit threshold. This means that the
current limit threshold is “reduced to around 4.2 A” as the
junction temperature increases above 160°C. When the
temperature is above 175°C, over-temperature shutdown
(latch-OFF) will occur. This combination of features allows
the device to continue operating for short periods of time (< 30
seconds) with unexpected loads, while still retaining
adequate protection for both the device and the load.
FUNCTIONAL PIN DESCRIPTION
POWER GROUND AND ANALOG GROUND
(PGND AND AGND)
The power and analog ground pins should be connected
together with a very low-impedance connection.
POSITIVE POWER SUPPLY (VPWR)
VPWR pins are the power supply inputs to the device. All
VPWR pins must be connected together on the printed circuit
board with as short as possible traces, offering as low an
impedance as possible between pins.
STATUS FLAG (SF)
This pin is the device fault status output. This output is an
active LOW open drain structure requiring a pull-up resistor
to V_DD. The maximum V_DD is < 7.0 V. Refer to Table 5, Truth
Table, page 15 for the SF Output status definition.
INPUT 1,2 AND DISABLE INPUT 1
(IN1, IN2, AND D1)
These pins are input control pins used to control the
outputs. These pins are 3.0 V/ 5.0 V CMOS-compatible
inputs with hysteresis. IN1 and IN2 independently control
OUT1 and OUT2, respectively. D1 input is used to tri-state
disable the H-bridge outputs.
When D1 is SET (D1 = logic HIGH) in the disable state,
outputs OUT1 and OUT2 are both tri-state disabled; however,
the rest of the device circuitry is fully operational and the
supply I_PWR(STANDBY) current is reduced to a few mA. Refer to
Table 3, Static Electrical Characteristics, page 6.
H-BRIDGE OUTPUT (OUT1, OUT2)
These pins are the outputs of the H-bridge with integrated
free-wheeling diodes. The bridge output is controlled using
the IN1, IN2, D1, and EN/D2 inputs. The outputs have PWM
current limiting above the I_LIM 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 t _b) is incorporated to distinguish
between load currents that are higher than the I_LIM 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/DISABLE INPUT 2 (EN/D2)
The EN/D2 pin performs the same function as D1 pin,
when it goes to a logic LOW the outputs are immediately tri-
stated. It is also used to place the device in a Sleep mode so
as to consume very low currents. When the EN/D2 pin
voltage is a logic LOW state, the device is in the Sleep mode.
Analog Integrated Circuit Device Data
Freescale Semiconductor
33931
11