CAT3200/3200-5

6

Doc. No. MD-5002, Rev. L

© Catalyst Semiconductor, Inc.

Characteristics subject to change without notice

resistor network (400k

Ω). The feedback network will

result in a reverse current of 10

µA to 20µA to flow back

through the device to ground.

Whenever the device is taken out of shutdown mode, the

output voltage will experience a slew rate controlled

power-up. Full operating voltage is typically achieved in

less than 0.5 msec.

GND is the ground reference for all voltages on CAT3200-

5 devices.

FB (CAT3200 Only) is the feedback input pin. An output

divider should be connected from OUT to FB to program

the output voltage.

PGND (CAT3200 Only). Is the same as GND for the

CAT3200-5 except for the internal reference connection

to SGND.

SGND (CAT3200 Only) Ground pin for the internal

reference. The CNEG connection is switched to this pin

during the normal charge pump operation.

PIN FUNCTIONS

IN is the power supply. During normal operation the

device draws a supply current which is almost constant.

A very brief interval of non-conduction will occur at the

switching frequency. The duration of the non-conduction

interval is set by the internal non-overlapping

“break-before-make” timing. IN should be bypassed

with a 1

µF to 4.7µF low ESR (Equivalent Series

Resistance) ceramic capacitor.

For filtering, a low ESR ceramic bypass capacitor (1

µF)

in close proximity to the IN pin prevents noise from being

injected back into the power supply.

SHDN

SHDN

SHDN

SHDN

SHDN is the logic control input (Active LOW) that places

the device into shutdown mode. The internal logic is

CMOS and the pin does not use an internal pull-down

resistor. The

SHDN

SHDN

SHDN

SHDN

SHDN pin should not be allowed to float.

CPOS, CNEG are the positive and negative connections

respectively for the charge pump flying capacitor. A low

ESR ceramic capacitor (1

µF) should be connected

between these pins. During initial power-up it may be

possible for the capacitor to experience a voltage reversal

and for this reason, avoid using a polarized (tantalum or

aluminum) flying capacitor.

OUT is the regulated output voltage to power the load.

During normal operation, the device will deliver a train of

current pulses to the pin at a frequency of 2MHz.

Adequate filtering on the pin can typically be achieved

through the use a low ESR ceramic bypass capacitor

(1

µF to 4.7µF) in close proximity to the OUT pin. The

ESR of the output capacitor will directly influence the

output ripple voltage.

When the shutdown mode is entered, the output is

immediately isolated from the input supply, however, the

output will remain connected to the internal feedback

CAT3200 Adjustable Output

CAT3200-5 5V Fixed Output

BLOCK DIAGRAM

+

—

EN

2MHz

Voltage

Doubler

1.25V

SGND

SHDN

IN

CNEG CPOS

2VIN

5V/100mA

OUT

PGND

FB

+

—

EN

2MHz

Voltage

Doubler

300k

100k

1.25V

GND

SHDN

IN

CNEG CPOS

2VIN

5V

100mA

OUT