2962 Ver la hoja de datos (PDF) - Allegro MicroSystems
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2962 Datasheet PDF : 8 Pages
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2962
DUAL PWM
SOLENOID/MOTOR DRIVER
CIRCUIT DESCRIPTION
AND APPLICATIONS INFORMATION
The UDN2962W high-current driver is intended for use as a
free-running, pulse-width modulated solenoid driver.
Circuit Description. In operation, the source and sink drivers are
both turned on by a low level at the input. The load current rises with
time as a function of the load inductance, total circuit resistance, and
supply voltage and is sensed by the external sense resistor (RS).
When the load current reaches the trip point (ITRIP), the comparator
output goes high and turns off the source driver. The actual load
current will peak slightly higher than ITRIP because of the internal logic
and switching delays.
After the source driver is turned off, the load current continues to
circulate through the sink driver and an internal ground clamp diode.
The rate of current decay is a function of the load inductance and total
circuit resistance.
Circuit Layout. To prevent interaction
between channels, each of the two high-level
power ground returns (the low side of the
sense resistors) must be returned independ-
ently to the low-level signal ground (pin 1).
The circuit common (pin 1) can then be
routed to the system ground.
The printed wiring board should utilize a
heavy ground plane. For optimum perform-
ance, the driver should be soldered directly
into the board.
The power supply (VCC) should be
decoupled with an electrolytic capacitor
(≥10 µF) as close as possible to pin 7.
An internal constant current sink reduces the trip point (hysteresis)
until the decaying load current reaches the lower threshold, when the
comparator output goes low and the source driver is again turned on.
Load current is again allowed to rise to the trip point and the cycle
repeats.
Maximum load current and hysteresis is determined by the user.
SUPPLY
R
S
1
3
7
10
R
+
S
Determining Maximum Load Current and Hysteresis. Trip
current (ITRIP) is determined as a function of resistance RS and the
threshold voltage, VTHS:
ITRIP = VTHS
10 RS
where VTHS = 10 x VSENSE = 0.6 V to 5.0 V.
Hysteresis percentage (H) is determined by resistance RH and is
independent of the load current:
H = RH
50 x VREF
The chopping frequency is asynchronous and a function of the
system and circuit parameters, including load inductance, supply
voltage, hysteresis setting, and switching speed of the driver.
Resistance RT is determined as:
RT = RHVTHS
VREF – VTHS
Note that if VTHS = VREF, then RT = ∞.
VIN
VSINK
VSOURCE
I LOAD
VTHS
Dwg. OP-001
TYPICAL WAVESHAPES
VCC
GND
VCC
GND
I TRIP • RS =VTHS 10
Dwg. WP-006
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000
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