Datasheet
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 MΩ 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 =
V
LOBATT
− 1. 25 V
1. 25 V
R2
⎛
⎝
⎜
⎞
⎠
⎟
−
V
L
− 1. 25 V
R
L
+ R
HYS
⎛
⎝
⎜
⎞
⎠
⎟
where V
L
is the logic power supply voltage, R
L
is the pull-up
resistor, and R
HYS
creates the hysteresis.
ADP1111
1.25V
REF
GND
AO
5V
R
L
47k
TO
PROCESSOR
R1
R2
V
BAT
V
IN
SET
R
HYS
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
C
L
33μF
OUTPUT
R3*
(OPTIONAL)
MBRS120T3
20μH
CTX20-4
(5V @ 100mA)
INPUT +3V
I
LIM
V
IN
SW2
SW1
SENSE
GNDSETAO
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.
I
LIM
V
IN
SW1
SW2
SENSE
GNDSETAO
ADP1111-5
NC
L1
C
L
22μF
D1
1N5818
R
LIM
100Ω
1
+
15μH
CTX15-4
INPUT
2 3
6
7 5
4
8
NC
OUTPUT
(9V
IN
TO 5V @ 150mA,
6.5V
IN
TO 5V @ 50mA)
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.
I
LIM
V
IN
SW1
SW2
SENSE
GNDSETAO
ADP1111-5
NC
L1
C
L
47μF
D1
1N5818
R
LIM
100Ω
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.
I
LIM
V
IN
SW1
SW2
GNDSETAO
ADP1111-5
NC
L1
C
L
33μF
D1
1N5818
R
LIM
100Ω
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
REV. A
I
LIM
V
IN
SW1
SW2
GNDSETAO
ADP1111-5
NC
L1
C
L
33μF
D1
1N5818
R
LIM
100Ω
1
+
33μH
CTX33-2
5V TO 25V
INPUT
2 3
6
7 5
4
8
NC
–5V
@ 75mA
SENSE