Datasheet

In its normal mode of operation (CLK/SEL = low), the
MAX1763 offers fixed-frequency PWM operation through
most of its load range. At light loads (less than 25% of full
load), the device automatically optimizes efficiency by
switching only as needed to supply the load. Shutdown
reduces quiescent current to just 1µA. Figure 2 shows
the standard application circuit for the MAX1763. (An
external Schottky diode is needed for output voltages
greater than 4V, or to assist low-voltage startup.)
Additional features include synchronous rectification for
high efficiency and increased battery life, and a gain
block that can be used to build a linear regulator using
an external P-channel MOSFET pass device. This gain
block can also function as a voltage-monitoring com-
parator. The MAX1763 is available in a 16-pin QSOP
package or a 1.5W 16-pin TSSOP-EP package for high-
temperature or high-dissipation applications.
MAX1763
1.5A, Low-Noise, 1MHz, Step-Up
DC-DC Converter
_______________________________________________________________________________________ 9
Figure 1. Functional Diagram
Figure 2. PFM/PWM Automode Connection
GAIN
BLOCK
AO
N
AIN
2.15V
IC POWER
1.25V
DUAL
MODE/
FB
REFERENCE
UNDERVOLTAGE LOCKOUT
STARTUP
OSCILLATOR
1MHz
OSCILLATOR
CONTROLLER
P
N
EN
D
EN
POUT
LX
PGND
OSC
MODE
FB
EN
Q
Q
Q
REF
FB
ISET
GND
CLK/SEL
ON RDY
REF
0.938V
ONB
ONA
OUT
MAX1763
ISET
GNDPGND
AO
POUT
OUT
AIN
LX
D1
MBR0520L
V
IN
0.7V TO 5.5V
C4
2 x 100μF
OUT
3.3V
L1
1.5μH
FB
REF
CLK/SEL
ONA
ONB
ISET
C3
0.22μF
C2
1.0μF
NOTE: HEAVY LINES INDICATE HIGH-CURRENT PATHS.
R5
4.7Ω
MAX1763
C1
47μF
Table 1. Typical Available Output Current
NUMBER
OF CELLS
INPUT
VOLTAGE
(V)
OUTPUT
VOLTAGE
(V)
OUTPUT
CURRENT
(mA)
1 NiCd/NiMH 1.2 3.3 675
2.4 3.3 1500
2 NiCd/NiMH
2.4 5.0 950
1 Li+ 2.7 (min) 3.3 1300
1 Li+ 2.7 (min) 5.0 1100
3 NiCd/NiMH 3.6 5.0 1600