SA50CE Datasheet, PDF (4/5 Pages) Cirrus Logic – H-BRIDGE MOTOR DRIVER/AMPLIFERS

SA50CE
Product Innova tionFrom
GENERAL
TYPICAL SYSTEM OPERATION
Please read Application Note 30 on "PWM Basics".
Refer to Application Note 1 "General Operating Con-
siderations" for helpful information regarding power
supplies, heat sinking and mounting. Visit www.Cirrus.
com for design tools that help automate pwm filter de-
sign and heat sink selection. The "Application Notes"
and "Technical Seminar" sections contain a wealth of
information on specific types of applications.Information
on package outlines, heat sinks, mounting hardware
and other accessories are located in the "Packages and
Accessories" section. Evaluation Kits are available for
most Apex Precision Power product models, consult
the "Evaluation Kit" section for details. For the most
current version of all Apex Precision Power product
data sheets, visit www.Cirrus.com.
+12V
+VS
22μF
R
6
Vcc
3
+VS
MOTOR A
4
SA50CE
8
INPUT
2
7
MOTOR B
GND
RSENSE A ₅
RSENSE B
1
SNUBBER NETWORK
100Ω
2W
1000pF
200V
MOTOR
MYLAR
6.8μF
100V
POLY
SENSE
RESISTORS
0.1Ω
NO OUTPUT
R
SWITCHING
+12V
PIN DESCRIPTION
V_CC - is the low voltage supply for powering internal
logic and drivers for the lowside and highside
MOSFETS.The supplies for the highside drivers
+12V
GND
ANALOG
INPUT
CURRENT
RIN
RDIVIDE
(VCC÷2)
RDIVIDE
RDIVIDE = 2X Rf
are derived from this voltage.
V_S - is the higher voltage H-bridge supply. The MOS-
FETS obtain the output current from this supply
Rf
RIN
pin. Proper by-passing to GND with sufficient
capacitance to suppress any voltage transients,
and to ensure removing any drooping during
switching, should be done as close to the pins
on the hybrid as possible.
A OUT - is the output pin for one half of the bridge. Increas-
ing the input voltage causes increasing duty cycle at
this output.
B OUT - is the output pin for the other half of the bridge.
Decreasing the input voltage causes increasing duty
cycles at this point.
RSENSE A - This is the connection for the bottom of the A
half bridge. This can have a sense resistor connected
to the V_S return ground for current limit sensing, or can
be connected directly to ground. The maximum voltage
on this pin is ±2 volts with respect to GND.
GND - is the return connection for the input logic and V_CC.
RSENSE B - This is the connection for the bottom of the B
half bridge. This can have a sense resistor connection
to the V_S return ground for current limit sensing, or can
be connected directly to ground. The maximum voltage
on this pin is ±2 volts with respect to GND.
INPUT - is an analog input for controlling the PWM pulse width
of the bridge. A voltage higher than V_CC /2 will produce
greater than 50% duty cycle pulses out of A OUT. A
voltage lower than V_CC /2 will produce greater than 50%
duty cycle pulses out of B OUT.
CURRENT CONTROL
This is a diagram of a typical application of the SA50CE.
The design Vcc voltage is +12 volts. V_CC is internally bypassed
with a good low ESR ceramic capacitor. A higher ESR bulk
capacitor, such as a tantalum electrolytic, may be used ex-
ternally in parallel. The analog input can be an analog speed
control voltage from a potentiometer, other analog circuitry or
by microprocessor and a D/A converter.This analog input gets
pulled by the current control circuitry in the proper direction
to reduce the current flow in the bridge if it gets too high. The
gain of the current control amplifier will have to be set to obtain
the proper amount of current limiting required by the system.
Current sensing is done in this case by a 0.1Ω sense resistor
to sense the current from both legs of the bridge separately. It
is important to make the high current traces as big as possible
to keep inductance down. The storage capacitor connected to
the V_S and the hybrid GND should be large enough to provide
the high energy pulse without the voltage sagging too far. A
low ESR capacitor will be required. Mount capacitor as close
to the hybrid as possible. The connection between GND and
the V_S return should not be carrying any motor current. The
sense resistor signal is common mode filtered as necessary
to feed the limiting circuitry. This application will allow full four
quadrant torque control for a closed loop servo system.
A snubber network is usually required, due to the inductance
in the power loop. It is important to design the snubber network
to suppress any positive spikes above +V_S and negative spikes
below –2V with respect to pin 7 (GND).
4
SA50CEU