Rainbow Electronics MAX1688 - Manual

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General Description
The MAX1687/MAX1688 step-up DC-DC converters deliv-
er up to 2W from a single Li-Ion or three NiMH cells. The
devices are ideal for burst-load applications such as GSM
cell phones and wireless LANs, where the RF power
amplifiers require short, high current bursts. The
MAX1687/MAX1688 reduce battery surge current by slow-
ly charging a reservoir capacitor, which supplies the nec-
essary peak energy for the load current burst. As a result,
the peak battery current is limited, thus maximizing battery
life and minimizing battery voltage sag and transient dips.
An internal synchronous rectifier provides over 90% con-
version efficiency and eliminates the need for an external
Schottky diode. A logic shutdown mode reduces the shut-
down current to only 3µA. The devices can be disabled
during current bursts (RF transmit mode) to eliminate
switching noise.
The switching frequency of the MAX1687/MAX1688, con-
trolled by the selected inductor, can exceed 1MHz. Two
external resistors set the output voltage from 1.25V to 6V.
The MAX1687 controls peak battery current, while the
MAX1688 features a more advanced, adaptive constant-
recharge-time algorithm that maximizes battery life. The
MAX1687/MAX1688 are available in thin 16-pin TSSOP
(1.1mm max height) or standard 8-pin SO packages.
Applications
GSM Phones
Wireless Handsets
PC Cards (PCMCIA)
Features
♦ Low 450mA Peak Battery Current
Provides 2A, 5V GSM Burst
♦ 90% Efficiency
♦ Internal Power MOSFETs and Current-Sense
Resistor
♦ Output Disconnects from Input During Shutdown
♦ 3µA Shutdown Current
♦ Precise Voltage-Controlled Current Limit
(MAX1687)
♦ Adaptive Constant-Recharge-Time Capability
(MAX1688)
♦ 1.25V to 6V Adjustable Output
♦ 2.7V to 6V Input Range
(1 Li-Ion cell or 3 NiMH cells)
♦ Switching Frequency Can Exceed 1MHz
♦ Standby Mode Disables DC-DC During
Transmission Burst
♦ Low Inrush Current at Start-Up
MAX1687
†
/MAX1688
†
Step-Up DC-DC Converters with
Precise, Adaptive Current Limit for GSM
________________________________________________________________ Maxim Integrated Products 1
16
15
14
13
12
11
10
9
1
2
3
4
5
6
7
8
IN OUT
OUT
LX2
LX2
PGND
PGND
AGND
ON
TOP VIEW
MAX1687
MAX1688
TSSOP
IN
LX1
FB
LX1
LIM [CHG]
REF
N.C.
[ ] ARE FOR MAX1688
MAX1687
MAX1688
V OUT
UP TO 6V
OUT
IN
LX1 LX2
ON
ON
2.7V TO 6V
OFF
0 TO 1V
CONTROL INPUT
1 Li-lon
OR
3 NiMH
OR
3 ALKALINE
(LIM)
REF
FB
[CHG]
( ) ARE FOR MAX1687
[ ] ARE FOR MAX1688
GND
Typical Operating Circuit
19-1426; Rev 0; 2/99
PART*
MAX1687 EUE
MAX1687ESA
MAX1688 EUE -40°C to +85°C
-40°C to +85°C
-40°C to +85°C
TEMP. RANGE PIN-PACKAGE
16 TSSOP
8 SO
16 TSSOP
Pin Configurations
Ordering Information
MAX1688ESA -40°C to +85°C 8 SO
Pin Configurations continued at end of data sheet.
† Patent pending
* U.S. and foreign patents pending.
EVALUATION KIT MANUAL
FOLLOWS DATA SHEET