ADP1111

–13–

REV. 0

The circuit of Figure 27b may produce multiple pulses when

approaching the trip point due to noise coupled into the SET

input. To prevent multiple interrupts to the digital logic,

hysteresis can be added to the circuit (Figure 27). Resistor

RHYS, with a value of 1 M

Ω to 10 MΩ, provides the hysteresis.

The addition of RHYS will change the trip point slightly, so the

new value for R1 will be:

R1

=

1.25 V

R2









−









ADP1111

1.25V

REF

GND

AO

5V

47k

TO

PROCESSOR

R1

R2

SET

33k

1.6M

Figure 27b.

APPLICATION CIRCUITS

All Surface Mount 3 V to 5 V Step-Up Converter

This is the most basic application (along with the basic step-

down configuration to follow) of the ADP1111. It takes full

advantage of surface mount packaging for all the devices used in

the design. The circuit can provide +5 V at 100 mA of output

current and can be operated off of battery power for use in

portable equipment.

+

L1

D1

33µF

OUTPUT

R3*

(OPTIONAL)

MBRS120T3

20µH

CTX20-4

(5V @ 100mA)

INPUT +3V

SW2

SW1

SENSE

GND

SET

AO

ADP1111-5

NC

1

2

6

7

5

3

8

NC

4

Figure 28. All Surface Mount +3 V to +5 V Step-Up Converter

9 V to 5 V Step-Down Converter

This circuit uses a 9 V battery to generate a +5 V output. The

circuit will work down to 6.5 V, supplying 50 mA at this lower

limit. Switch current is limited to around 500 mA by the 100

Ω

resistor.

SW2

SENSE

GND

SET

AO

ADP1111-5

NC

L1

22µF

D1

1N5818

100

Ω

1

+

15µH

CTX15-4

INPUT

2

3

6

7

5

4

8

NC

OUTPUT

9V

Figure 29. 9 V to 5 V Step-Down Converter

20 V to 5 V Step-Down Converter

This circuit is similar to Figure 29, except it supplies much

higher output current and operates over a much wider range of

input voltage. As in the previous examples, switch current is

limited to 500 mA.

SW2

SENSE

GND

SET

AO

ADP1111-5

NC

L1

47µF

D1

1N5818

100

Ω

1

+

68µH

CTX68-4

12V TO 28V

INPUT

2

3

6

7

5

4

8

NC

OUTPUT

(+5V @ 300mA)

Figure 30. 20 V to 5 V Step-Down Converter

+5 V to –5 V Converter

This circuit is essentially identical to Figure 22, except it uses a

fixed-output version of the ADP1111 to simplify the design

somewhat.

SW2

GND

SET

AO

ADP1111-5

NC

L1

33µF

D1

1N5818

100

Ω

1

+

33µH

CTX33-2

12V TO 28V

INPUT

2

3

6

7

5

4

8

NC

–5V

@ 75mA

SENSE

Figure 31. +5 V to –5 V Converter