SA60 Datasheet, PDF (5/6 Pages) Cirrus Logic – H-BRIDGE MOTOR DRIVER/AMPLIFIERS

Product Innova tionFrom
SA60
GENERAL
Please read Application Note 30 on "PWM Basics". Refer to Application Note 1 "General Operating Considerations"
for helpful information regarding power supplies, heat sinking and mounting. Visit www.apexmicrotech.com for
design tools that help automate pwm filter design; heat sink selection; Apex’s complete Application Notes library;
Technical Seminar Workbook; and Evaluation Kits.
PWM OSCILLATOR – INTERNAL OR EXTERNAL
The SA60 contains an internal PWM oscillator whose frequency is determined by an external capacitor connected
between pin 1 and pin 2. Maximum frequency is 125 kHz. The user may also disregard the internal PWM oscillator
and supply the SA60 with an external TTL pulse generator up to 250KHZ.
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 are derived from this voltage.
V_S - is the higher voltage H-bridge supply. The MOSFETS obtain the output current from this supply pin. The voltage
on this pin is limited to +80V by the drive IC. The MOSFETS are rated at 100 volts.
ISENSE A & B - These are tied to power gnd directly or through sense resistors.
ANALOG GND - is the reference for the internal PWM oscillator. Connect this pin to pin 6. Connect low side of Vcc
supply and any other supply used to generate analog input signals to ANALOG GND.
ANALOG INPUT - is an analog input for controlling the PWM pulse width of the bridge. A voltage higher than Vcc/2
will produce greater than 50% duty cycle pulses out of B OUT. A voltage lower than Vcc/2 will produce greater
than 50% duty cycle pulses out of A OUT. If using in the digital mode, bias this point at 1/2 the logic high level.
DISABLE - Is the connection for disabling all 4 output switches. DISABLE high overrides all other inputs. When
taken low, everything functions normally. An internal pullup to Vcc will keep DISABLE high if pin left open.
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:


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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
SA60U