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MAX1687ESAMAXIMN/a1254avaiStep-Up DC-DC Converters with Precise / Adaptive Current Limit for GSM
MAX1687EUEMAXIMN/a709avaiStep-Up DC-DC Converters with Precise / Adaptive Current Limit for GSM
MAX1688EUEMAXIMN/a43avaiStep-Up DC-DC Converters with Precise / Adaptive Current Limit for GSM
MAX1688EUEMAXN/a12avaiStep-Up DC-DC Converters with Precise / Adaptive Current Limit for GSM


MAX1687ESA ,Step-Up DC-DC Converters with Precise / Adaptive Current Limit for GSMfeatures a more advanced, adaptive constant-recharge-time algorithm that maximizes battery life. Th ..
MAX1687EUE ,Step-Up DC-DC Converters with Precise / Adaptive Current Limit for GSMapplications such as GSM ' 90% Efficiencycell phones and wireless LANs, where the RF power' Interna ..
MAX1687EUE+T ,Step-Up DC-DC Converters with Precise, Adaptive Current Limit for GSMfeatures a more advanced, adaptive constant-recharge-time algorithm that maximizes battery life. Th ..
MAX1688ESA+ ,Step-Up DC-DC Converters with Precise, Adaptive Current Limit for GSMapplications such as GSM ♦ 90% Efficiencycell phones and wireless LANs, where the RF power♦ Interna ..
MAX1688EUE ,Step-Up DC-DC Converters with Precise / Adaptive Current Limit for GSMFeatures' Low 450mA Peak Battery Current The MAX1687/MAX1688 step-up DC-DC converters deliv-Provide ..
MAX1688EUE ,Step-Up DC-DC Converters with Precise / Adaptive Current Limit for GSMELECTRICAL CHARACTERISTICS(V = V = +3V, V = 1V (MAX1687), V = 1V (MAX1688), V = 1.5V, V = 6V, T = 0 ..
MAX4489ASA+ ,SOT23, Low-Noise, Low-Distortion, Wide-Band, Rail-to-Rail Op Ampsfeatures make the devices an idealchoice for
MAX4489ASA+T ,SOT23, Low-Noise, Low-Distortion, Wide-Band, Rail-to-Rail Op AmpsApplicationsOrdering InformationADC BuffersPIN- TOPDAC Output AmplifiersPART TEMP RANGEPACKAGE MARK ..
MAX4489AUA ,42 MHz, Low-noise, low-distortion, SOT23, wide-band, rail to rail op amp.Applications  Available in Space-Saving SOT23, µMAX, andTSSOP PackagesADC BuffersDAC Output Amplif ..
MAX4489AUA+ ,SOT23, Low-Noise, Low-Distortion, Wide-Band, Rail-to-Rail Op Ampsfeatures make the devices an idealchoice for
MAX4489AUA+ ,SOT23, Low-Noise, Low-Distortion, Wide-Band, Rail-to-Rail Op AmpsELECTRICAL CHARACTERISTICS(V = +5V, V = 0V, V = 0V, V = V /2, R tied to V /2, SHDN = V , T = -40°C ..
MAX4489AUA+T ,SOT23, Low-Noise, Low-Distortion, Wide-Band, Rail-to-Rail Op AmpsApplicationsOrdering InformationADC BuffersPIN- TOPDAC Output AmplifiersPART TEMP RANGEPACKAGE MARK ..


MAX1687ESA-MAX1687EUE-MAX1688EUE
Step-Up DC-DC Converters with Precise / Adaptive Current Limit for GSM
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% EfficiencyInternal Power MOSFETs and Current-Sense
Resistor
Output Disconnects from Input During Shutdown3µA Shutdown CurrentPrecise 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 1MHzStandby 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
Typical Operating Circuit
Pin Configurations
Ordering Information

†Patent pending
*U.S. and foreign patents pending.
MAX1687/MAX1688
Step-Up DC-DC Converters with
Precise, Adaptive Current Limit for GSM
ABSOLUTE MAXIMUM RATINGS
ELECTRICAL CHARACTERISTICS

(VIN= VON= +3V, VLIM= 1V (MAX1687), VCHG= 1V (MAX1688), VFB= 1.5V, VOUT= 6V, TA = 0°C to +85°C, unless otherwise noted.
Typical values are at TA= +25°C.)
Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional
operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to
absolute maximum rating conditions for extended periods may affect device reliability.
IN, ON, LX1, CHG, LIM, FB, OUT, REF to GND.......-0.3V to +7V
LX2 to GND..............................................................-0.3V to +8V
IN, LX1 Average Current..........................................................1A
Continuous Power Dissipation (TA= +70°C)
TSSOP (derate 5.7mW/°C above +70°C)....................457mW
SO (derate 5.88mW/°C above +70°C).........................471mW
Operating Temperature Range...........................-40°C to +85°C
Storage Temperature Range.............................-65°C to +150°C
Lead Temperature (soldering, 10sec)............................+300°C
MAX1687/MAX1688
Step-Up DC-DC Converters with
Precise, Adaptive Current Limit for GSM
ELECTRICAL CHARACTERISTICS

(VIN= VON= +3V, VLIM= 1V (MAX1687), VCHG= 1V (MAX1688), VFB= 1.5V, VOUT= 6V, TA= -40°C to +85°C, unless otherwise noted.)
(Note 1)
Note 1:
Specifications to -40°C are guaranteed by design, not production tested.
Typical Operating Characteristics

(VIN= +3.3V, VOUT= 5V, VLIM = 1V, Figures 6b and 7, TA= +25°C, unless otherwise noted.)
MAX1687/MAX1688
Step-Up DC-DC Converters with Precise,
Adaptive Current Limit for GSM

_____________________________Typical Operating Characteristics (continued)
(VIN= +3.3V, VOUT= 5V, VLIM = 1V, Figures 6b and 7, TA= +25°C, unless otherwise noted.)
MAX1687/MAX1688
Step-Up DC-DC Converters with
Precise, Adaptive Current Limit for GSMypical Operating Characteristics (continued)

(VIN= +3.3V, VOUT= 5V, VLIM = 1V, Figures 6b and 7, TA= +25°C, unless otherwise noted.)
MAX1687/MAX1688
Detailed Description

The MAX1687 and MAX1688 ICs supply power ampli-
fiers inGSM applications where limited input current
surge is desirable. For example, GSM systems require
high-power, 12% duty-cycle RF bursts. Synchronizing
the MAX1687/MAX1688 to enter standby mode during
these RF bursts eliminates battery surge current and
minimizes switching noise to the power amplifier. In
standby mode, the charged output reservoir capacitor
delivers power to the power amplifier. Between each
burst, the DC-DC converter switches on to charge the
output capacitor. To improve efficiency and reduce peak
battery current, the MAX1687/MAX1688 provide a volt-
age-controlled current limit. The MAX1688 is a MAX1687
with added self-regulating circuitry that recharges the
reservoir capacitor in a fixed time (Figure 1).
Start-Up Sequence

In a conventional DC-DC converter, when high current
is required by the load, the battery voltage droops due
to battery series resistance. This may cause other cir-
cuitry that depends on the battery to malfunction or be
reset. The MAX1687/MAX1688 prevent battery voltage
droop by charging the reservoir capacitor during sys-
tem off-time and isolate the battery from the output dur-
ing high current demand. The MAX1687/MAX1688 are
gentle to the battery during initial power-up, as well.
Step-Up DC-DC Converters with
Precise, Adaptive Current Limit for GSM
Pin Description
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