5 V/1 2 V/1 5 V o r Ad ju s t a b le , High-Effic ie nc y,
Low I , Ste p-Up DC-DC Controlle rs
Q
VIN = 5V
VIN = 3V
C2
C2
0.1µF
0.1µF
2
2
V+
V+
C1
100µF
5
4
3
6
C1
68µF
5
4
3
6
REF
REF
C3
C3
0.1µF
L1
22µH
L1
22µH
0.1µF
MAX770
MAX771
D1
1N5817
D1
1N5817
V
OUT
= 12V
V
= 5V
@ 1A
OUT
SHDN
SHDN
@ 0.5A
1
8
1
8
N
N
FB
EXT
CS
FB
EXT
CS
MTP3055EL
Si9410DY
AGND
AGND
R
75mΩ
C4
300µF
R
C4
200µF
SENSE
SENSE
GND
7
GND
7
100mΩ
0–MAX73
Figure 2a. 5V Preset Output, Bootstrapped
Figure 2b. 12V Preset Output, Bootstrapped
V
IN
= 4V
VIN = 5V
C2
0.1µF
C1
68µF
C2
0.1µF
C1
47µF
2
2
L1
20µH
L1
22µH
V+
V+
V
= 12V
@ 0.5A
D1
1N5817
D1
1N5817
OUT
5
5
4
6
REF
REF
V
= 9V
OUT
C3
C3
0.1µF
0.1µF
MAX770
MAX771
MAX772
C4
100µF
MAX770
MAX771
MAX772
1
8
3
C4
200µF
1
8
4
6
N
N
SHDN
AGND
EXT
CS
SHDN
AGND
EXT
CS
Si9410DY
R
SENSE
R
R2
140k
SENSE
R2
127k
100mΩ
3
FB
FB
GND
7
GND
7
R1
28k
R1
18k
R2 = (R1) (VV -1)
R2 = (R1) (VV -1)
OUT
OUT
REF
REF
V
= 1.5V
V
= 1.5V
REF
REF
Figure 2c. 12V Output, Non-Bootstrapped
Figure 2d. 9V Output, Bootstrapped
frequencies (up to 300kHz), allowing the use of tiny
external components.
minimum off-time (2.3µs); there is no oscillator. Once
off, the minimum off-time one-shot holds the switch
off for 2.3µs. After this minimum time, the switch either
1) stays off if the output is in regulation, or 2) turns on
again if the output is out of regulation.
As with traditional PFM converters, the power transistor
is not turned on until the voltage comparator senses
that the output is out of regulation. However, unlike tra-
ditional PFM converters, the MAX770–MAX773 switch
using the combination of a peak current limit and a pair
of one-shots that set the maximum on-time (16µs) and
The control circuitry allows the ICs to operate in contin-
uous-conduction mode (CCM) while maintaining high
efficiency with heavy loads. When the power switch is
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10
MAXIM [ MAXIM INTEGRATED PRODUCTS ]
