ML4825

6

Figure 6. Open Loop Frequency Response

FREQUENCY (Hz)

100

10k

10M

1k

100k

100M

1M

100

80

60

40

20

0

–20

0

–90

–180

0

AV

0

OUT A

OUT B

POWER

GND

13

11

14

12

Q2

Q1

3

2

1

0

IOUT (A)

0

1.5

1.0

0.5

SINK

SOURCE

Figure 7. Simplified Schematic

Figure 8. Saturation Curves

ERROR AMPLIFIER

The ML4825 error amplifier is a 5.5MHz bandwidth 12V/

µs

slew rate op-amp with provision for limiting the positive

output voltage swing (Output Inhibit line) for ease in

implementing the soft start function.

OUTPUT DRIVER STAGE

The ML4825 Output Driver is a 2A peak output high

speed totem pole circuit designed to quickly switch the

gates of capacitive loads, such as power MOSFET

transistors.

SOFT START AND CURRENT LIMIT

The ML4825 employs two current limits. When the

immediately shut off and the cycle is terminated for the

remainder of the oscillator period by resetting the RS flip

flop.

If the output current is rising quickly such that the voltage

off, a soft start cycle is initiated. The soft start capacitor is

discharged and outputs are held “off” until the voltage at

SS reaches 1V, ensuring a complete soft start cycle. The

duty cycle on start up is limited by limiting the output

voltage of the error amplifier voltage to the voltage at SS.

5

4

3

2

1

TIME (

µs)

0

0.2

0.6

1.0

0.8

0.4

Figure 5. Unity Gain Slew Rate