SA60_10 Datasheet, PDF (5/6 Pages) Cirrus Logic – H-Bridge Motor Driver/Amplifiers

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Product Innovation From
SA60
PWM INPUT -Is the TTL compatible digital input for controlling the PWM pulse width of the bridge. A duty cycle
greater than 50% will produce greater than 50% duty cycle pulses out of the A out. A duty cycle less than 50%
will produce greater than 50% duty cycle from the B out. For analog inputs, the integration capacitor for the
internal clock must be connected between this pin and analog ground. The internal switching frequency is pro-
grammable up to 125 kHz by selection of the integration capacitor. The formula is:
( ) ^{CF (pF) =}
1.44 x10⁷
Fsw
– 50
BYPASSING
Adequate bypassing of the power supplies is required for proper operation. Failure to do so can cause erratic and
low efficiency operation as well as excessive ringing at the outputs. The Vs supply should be bypassed with at
least a 1µF ceramic capacitor in parallel with another low ESR capacitor of at least 10µF per amp of output current.
Capacitor types rated for switching applications are the only types that should be considered. The 1µF ceramic
capacitor must be physically connected directly to the Vs and POWER GND pins. Even one inch of lead length will
cause excessive ringing at the outputs. This is due to the very fast switching times and the inductance of the lead
connection. The bypassing requirements of the Vcc supply are less stringent, but still necessary. A .1µF to .47µF
ceramic capacitor connected directly to the Vcc and ANALOG GND pins will suffice.
PCB LAYOUT
The designer needs to appreciate that the SA60 combines in one circuit both high speed high power switching and
low level analog signals. Certain layout rules of thumb must be considered when a circuit board layout is designed
using the SA60:
1. Bypassing of the power supplies is critical. Capacitors must be connected directly to the power supply pins with
very short lead lengths (well under 1 inch). Ceramic chip capacitors are best.
2. Connect ANALOG GND to POWER GND with a conductor having no intermediate connections.Connect all Vs
power supply, filter and load related ground connections to POWER GND keeping these conductors separate
until reaching pin 6.Connect all Vcc power supply and input signal related ground connections to ANALOG
GND keeping conductors separate until reaching pin 1. Do not allow ground loops toform by making additional
ground connections at the low side of the physical power supplies. If ground plane is used do not allow more
than 1mA to flow through it.
3. Beware of capacitive coupling between output connections and signal inputs through the parasitic capacitance
between layers in multilayer PCB designs.
4. Do not run small signal traces between the pins of the output section (pins 8-12).
CURRENT SENSE
There are two load current sensing pins, I SENSE A and I SENSE B. The two pins can be shorted to POWER GND
in the voltage mode connection but both must be used in the current mode connection. It is recommended that R
SENSE resistors be non-inductive. Load current flows in the I SENSE pins. The SA60 has no internal currentlimit.
TRANSIENT SUPPRESSION
An RC network of a 100 pF Capacitor and a one ohm resistor is required as shown in the external connection dia-
gram on page 1. This network assures proper operation under various loads. Minimal power is dissipated in the
resistor.
SA60U
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