Rainbow Electronics MAX1703 - Manual (Page 8)

MAX1703
1-Cell to 3-Cell, High-Power (1.5A),
Low-Noise, Step-Up DC-DC Converter
8 _______________________________________________________________________________________
_______________Detailed Description
The MAX1703 is a highly efficient, low-noise power
supply for portable RF and data-acquisition instru-
ments. It combines a boost switching regulator, N-
channel power MOSFET, P-channel synchronous
rectifier, precision reference, shutdown control, versa-
tile gain block, and power-good (POK) comparator
(Figure 1) in a 16-pin narrow SO package.
The switching DC-DC converter boosts a 1- to 3-cell
input to a fixed 5V or an adjustable output between
2.5V and 5.5V. Typically the MAX1703 starts from a
low, 0.9V input and remains operational down to 0.7V.
The MAX1703 is optimized for use in cellular phones
and other applications requiring low noise during full-
power operation, as well as low quiescent current for
maximum battery life in low-power mode and shut-
down. It features constant-frequency (300kHz), low-
noise PWM operation with up to 1.5A output capability.
See Table 1 for typical outputs. A low-quiescent-cur-
rent, low-power mode offers an output up to 150mA
and reduces quiescent power consumption to 300µW.
In shutdown mode, the quiescent current is further
reduced to just 1µA. Figure 2 shows the standard appli-
cation circuit for the MAX1703.
2.15V
IC POWER
1.25V
DUAL
MODE/
FB
OUT
REFERENCE
UNDERVOLTAGE LOCKOUT
START-UP
OSCILLATOR
300kHz
OSCILLATOR
PFM/PWM
CONTROLLER
PFM/PWM
P
N
EN D
EN
POUT
LXN
LXP
PGND
COMPARATOR
OSC
MODE
FB
EN
Q Q
Q
OUT
REF
FB
POKIN
GND
CLK/SEL
ON RDY
REF
REF
ON
OUT
MAX1703
POK
N
GAIN
BLOCK
REF
AO
N
AIN
Figure 1. Functional Block Diagram