UDN2961B Allegro Microsystems Inc, UDN2961B Datasheet - Page 4

• Manufacturer Part Number: UDN2961B
• Manufacturer: Allegro Microsystems Inc

Specifications of UDN2961B

• Lead Free Status / RoHS Status: Not Compliant

half-bridge designed to drive a number of
inductive loads such as printer solenoids,
stepper motors, and dc motors. Load current
is sensed internally and is controlled by
pulse-width modulating (PWM) the output
driver(s) in a fixed off-time, variable-
frequency format. The peak current level is
set by the user’s selection of a reference
voltage. A slow current-decay mode
(chopping only the source driver) or a fast
current-decay mode (chopping both the
source and sink drivers) can be selected via
the MODE pin.
current-control circuitry into the slow-decay
mode. The RS flip-flop is set initially, and
both the source driver and the sink driver are
turned ON when the INPUT pin is at a logic
low. As current in the load increases, it is
sensed by the internal sense resistor until the
sense voltage equals the trip voltage of the
comparator. At this time, the flip-flop is reset
and the source driver is turned OFF. Over the
range of V
current trip point transfer function is a direct
linear function of the reference voltage:
( 10%), an external 2940
(R
will be slightly higher than the trip point
(especially for low-inductance loads) because
of the internal logic and switching delays
(typically 1.5 s). After the source driver turns
OFF, the load current decays, circulating
through an external ground clamp diode, the
load, and the sink transistor. The source
driver’s OFF time (and therefore the magni-
tude of the current decrease) is determined
by the one-shot’s external RC timing compo-
nents:
2961
HIGH-CURRENT
HALF-BRIDGE
PRINTHEAD/MOTOR DRIVER
CV
The UDN2961B/W is a high current
A logic low on the MODE pin sets the
To ensure an accurate chop current level
) is used. The actual load current peak
REF
= 0.8 V to 3.4 V, the output
I
TRIP
t
OFF
= V
= RC
REF
1% resistor
within the range of 20 k
one-shot times out, the flip-flop is set again, the source driver is re-
enabled, and the load current again is allowed to rise to the set peak
value and trip the comparator. This cycle repeats itself, maintaining the
average load current at the desired level.
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 [phone]
CURRENT
ENABLE
INPUT
MODE
LOAD
CIRCUIT
+
-
REF
I
V
TRIP
SENSE
V
BB
to 100 k
V
BB
RECIRCULATION (SLOW-DECAY MODE)
RECIRCULATION (FAST-DECAY MODE)
DRIVE CURRENT
RC
and 100 pF to 1000 pF. When the
RC/2
Dwg. EP-037
Dwg. WP-015