THEORY OF OPERATION

PEAK CURRENT REDUCTION

OFF

SWITCHED

Step-Down(Buck)Mode

OFF

ON

C

PUMP

Q

1

Q

3

Q

2

Q

4

C

IN

C

OUT

V

OUT

V

IN

Step-Up(Boost)Mode

(A)

(B)

OFF

ON

ON

OFF

C

PUMP

Q

2

Q

4

C

OUT

V

OUT

C

PUMP

Q

2

Q

4

C

OUT

V

OUT

OFF

ON

Q

1

Q

3

ON

OFF

Q

1

Q

3

C

IN

V

IN

C

IN

V

IN

REG710

During the second half cycle the FET switched are

The REG710 regulated charge pump provides a

configured as shown in Figure 19B, and the voltage

regulated output voltage for input voltages ranging

from less than the output to greater than the output.

regulated by skipping clock cycles as necessary.

This is accomplished by automatic mode switching

within the device. When the input voltage is greater

than the required output, the unit functions as a

variable

frequency

switch-mode

regulator.

This

In normal operation, the charging of the pump and

output capacitors usually leads to relatively high peak

input currents which can be much higher than that of

needed to maintain a regulated output voltage.

the average load current. The regulator incorporates

circuitry to limit the input peak current, lowering the

When the input voltage is less than the required

total EMI production of the device and lowering

output voltage, the device switches to a step-up or

output voltage ripple and input current ripple. Input

boost mode of operation, as shown in Figure 19.

A conversion clock of 50% duty cycle is generated.

by input current peaks.

During the first half cycle the FET switches are

Figure 18. Simplified Schematic of the REG710 Operating in the Step-Down Mode

Figure 19. Simplified Schematic of the REG710 Operating in the Step-Up or Boost Mode

8

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Product Folder Link(s): REG710