CAT3200, CAT3200−5

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6

Block Diagram

Figure 15. CAT3200 Adjustable Output

Figure 16. CAT3200−5 5 V Fixed Output

+

EN

2 MHz

Voltage

Doubler

1.25 V

SGND

IN

5 V / 100 mA

OUT

PGND

FB

+

EN

2 MHz

Voltage

Doubler

300 k

100 k

1.25 V

GND

IN

5 V

100 mA

OUT

CNEG CPOS

−

SHDN

−

SHDN

CNEG CPOS

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

mF to 4.7 mF low

ESR (Equivalent Series Resistance) ceramic capacitor

For filtering, a low ESR ceramic bypass capacitor (1

mF)

in close proximity to the IN pin prevents noise from being

injected back into the power supply.

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 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

mF) 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 2 MHz. Adequate

filtering on the pin can typically be achieved through the use

a low ESR ceramic bypass capacitor (1

mF to 4.7 mF) 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

resistor network (400 k

W). The feedback network will result

in a reverse current of 10

mA to 20 mA 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.