CS51031

http://onsemi.com

4

Q

Q

Q

Q

RG

PGND

R

S

F2

Flip–Flop

G2

+

–

Comparator

A6

1.25 V

G1

0.7 V

Hold Off

Comp

Fault

Comp

1.15 V

A4

CS Charge

Sense

Comparator

R

S

F1

Slow Discharge

Flip–Flop

GND

G4

G5

–

+

A3

Slow Discharge

Comparator

2.3 V

2.4 V

+

–

A2

CS

Comparator

2.5 V

1.5 V

55

5

CS

G3

2.5 V

1.5 V

A1

3.3 V

Oscillator

Comparator

Figure 2. Block Diagram

CIRCUIT DESCRIPTION

THEORY OF OPERATION

Control Scheme

The CS51031 monitors the output voltage to determine

reference voltage of 1.25 V during the oscillator’s charge

cycle, the PFET is turned on and remains on for the duration

of the charge time. The PFET gets turned off and remains off

during the oscillator’s discharge time with the maximum

duty cycle to 80%. It requires 7.0 mV typical, and 20 mV

method of control does not require any loop stability

compensation.