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Axelite Confidential Materials, do not copy or distribute without written consent.

Rev.1.9 Aug.05, 2010

AX3101



APPLICATION CIRCUIT

C2

470uF

C4

470uF

1

2

L1

33uH

R1

6.8K

R2

1.3K

VIN+12V

ON/OFF

C1

1nF

VOUT = 5V/2A

R3

1.3K

R4

100K

D1

B340

C8

0.1uF

FB

1

EN

2

OCSET

3

VCC

4

SW

5

SW

6

VSS

7

VSS

8

AX3101

R1

R2

VFB = 0.8V ; R2 suggest 0.8K ~ 6k

VOUT = VFB x (1 +

)

C3

0.1uF

Option

L1 recommend value (VIN=12V ,IOUT=2A,)

VOUT

1.8 V

2.5V

3.3V

5V

L1 Value

18uH

22uH

27uH

33uH



FUNCTION DESCRIPTIONS

WM Control

The AX3101 consists of DC/DC converters that employ a pulse-width modulation

(PWM) system. In converters of the AX3101, the pulse width varies in a range from 0 to

100%, according to the load current. The ripple voltage produced by the switching can

easily be removed through a filter because the switching frequency remains constant.

Therefore, these converters provide a low-ripple power over broad ranges of input voltage

and load current.

RDS (ON) Current Limiting

The current limit threshold is setting by the external resistor (R3) connecting from VCC

supply to OCSET pin. The internal 130uA sink current crossing the resistor sets the voltage

at pin of OCSET. When the PWM voltage is less than the voltage at OCSET, an

over-current condition is triggered. Please refer to the formula for setting the minimum

current limit value:

R

I

I

DS(ON)

OCSET

.

R3

SW(MIN)

08

0







(Normally, The ISW(MIN) setting more than IOUT 1.0A ).

Example:

ISW = (0.13mA x 1.3k + 0.08)/ 0.070Ω= 3.56A - (VIN=12V)

ISW = (0.13mA x 2.5K + 0.08)/ 0.10Ω= 4.05A - (VIN=5V)