MAX1703 Maxim, MAX1703 Datasheet - Page 8

• Manufacturer Part Number: MAX1703
• Description: 1-Cell to 3-Cell / High-Power 1.5A / Low-Noise / Step-Up DC-DC Converter
• Manufacturer: Maxim

Figure 1. Functional Block Diagram
1-Cell to 3-Cell, High-Power (1.5A),
Low-Noise, Step-Up DC-DC Converter
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.
8
_______________Detailed Description
_______________________________________________________________________________________
CLK/SEL
POKIN
OUT
GND
REF
AIN
ON
FB
OUT
2.15V
IC POWER
1.25V
ON
REF
REFERENCE
UNDERVOLTAGE LOCKOUT
RDY
MODE/
DUAL
OUT
FB
REF
REF
COMPARATOR
EN
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.
EN
OSCILLATOR
GAIN
BLOCK
300kHz
OSCILLATOR
START-UP
PFM/PWM
Q
MAX1703
D
EN
OSC
MODE
FB
CONTROLLER
PFM/PWM
Q
Q
N
N
N
P
POUT
LXN
PGND
POK
AO
LXP