P r o d u c t I n n o v a t i o n F r o m

SA07



SA07U

INTEGRATOR

The integrator provides the inverted signal for negative feedback and also the open loop gain for the overall applica-

tion circuit accuracy. Recommended value of C

the circuit for overall loop stability as required.

CURRENT LIMIT

There are two load current sensing pins, I SENSE A and I SENSE B. The two pins can be shorted in the voltage

mode connection but both must be used in the current mode connection (see figures A and B). It is recommended

that R

connect the I LIMIT/SHDN pin directly to the R

and connect the R

Switching noise spikes will invariably be found at the I SENSE pins. The noise spikes could trip the current limit

threshold which is only 100 mV. R

low 100 mV to prevent false current limiting. The sum of the DC level plus the noise peak will determine the current

limiting value. As in most switching circuits it may be difficult to determine the true noise amplitude without careful

attention to grounding of the oscilloscope probe. Use the shortest possible ground lead for the probe and connect

exactly at the GND terminal of the amplifier. Suggested starting values are C

0

The required value of R

R

where R

value of each R

it will further divide down the sense voltage. The shutdown divider network will also have an effect on the filtering

circuit.

SHUTDOWN

The shutdown circuitry makes use of the internal current limiting circuitry. The two functions may be externally

combined in voltage and current modes as shown below in Figures A and B. The R

very low values and can be considered zero for this application. In Figure A, R

the shutdown signal. After a suitable noise filter is designed for the current limit, adjust the value of R

minimum 110 mV of shutdown signal at the I LIMIT/SHDN pin when the shutdown signal is high. Note that C

filter both the current limit noise spikes and the shutdown signal. Shutdown and current limit operate on each cycle

of the internal switching rate. As long as the shutdown signal is high the output will be disabled.