MAX1706EEE-T Maxim Integrated Products, MAX1706EEE-T Datasheet - Page 10

• Manufacturer Part Number: MAX1706EEE-T
• Description: DC/DC Switching Controllers 1-3 Cell Step-Up w/Linear Regulator
• Manufacturer: Maxim Integrated Products

The MAX1705/MAX1706 are designed to supply both
power and low-noise circuitry in portable RF and data-
acquisition instruments. They combine a linear regula-
tor, step-up switching regulator, n-channel power
MOSFET, p-channel synchronous rectifier, precision
reference, and low-battery comparator in a single 16-
pin QSOP package (Figure 1). The switching DC-DC
converter boosts a 1- or 2-cell input to an adjustable
output between 2.5V and 5.5V. The internal low-dropout
regulator provides linear postregulation for noise-
sensitive circuitry, as well as outputs from 1.25V to
300mV below the switching-regulator output. The
MAX1705/MAX1706 start from a low, 1.1V input and
remain operational down to 0.7V.
These devices are optimized for use in cellular phones
and other applications requiring low noise during full-
power operation, as well as low quiescent current for
1- to 3-Cell, High-Current, Low-Noise,
Step-Up DC-DC Converters with Linear Regulator
Figure 1. Functional Diagram
10
CLK/SEL
FBLDO
TRACK
______________________________________________________________________________________
LBO
LBN
OUT
GND
ONA
REF
LBP
ONB
FB
2.15V
V
IC PWR
OUT
- 300mV
Detailed Description
V
LDO
ON
REFERENCE
1.250V
N
RDY
SHUTDOWN
THERMAL
SENSOR
LOGIC
maximum battery life during standby and shutdown.
They feature constant-frequency (300kHz), low-noise
pulse-width-modulation (PWM) operation with 300mA or
730mA output capability from 1 or 2 cells, respectively,
with 3.3V output. A low-quiescent-current standby
pulse-frequency-modulation (PFM) mode offers an out-
put up to 60mA and 140µA, respectively, and reduces
quiescent power consumption to 500µW. In shutdown
mode, the quiescent current is further reduced to just
1µA. Figure 2 shows the standard application circuit for
the MAX1705 configured in high-power PWM mode.
Additional features include synchronous rectification for
high efficiency and improved battery life, and an
uncommitted comparator for low-battery detection. A
CLK/SEL input allows frequency synchronization to
reduce interference. Dual shutdown controls allow shut-
down using a momentary pushbutton switch and micro-
processor control.
REF
EN
EN
OSCILLATOR
300kHz
OSCILLATOR
START-UP
ERROR
AMP
PFM/PWM
Q
MOSFET DRIVER
WITH CURRENT
D
EN
IFB
OSC
MODE
IREF
LIMITING
CONTROLLER
PFM/PWM
MAX1705
MAX1706
ICS
Q
Q
OUT
N
P
P
POUT
PGND
LDO
LX