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MAX1684EEEMAXIMN/a181avaiLow-Noise / 14V Input / 1A / PWM Step-Down Converters
MAX1684EEEMAXIM ?N/a867avaiLow-Noise / 14V Input / 1A / PWM Step-Down Converters
MAX1684EEEMAXN/a12avaiLow-Noise / 14V Input / 1A / PWM Step-Down Converters
MAX1685EEEMAXIMN/a2500avaiLow-Noise / 14V Input / 1A / PWM Step-Down Converters
MAX1685EEEMAXN/a19avaiLow-Noise / 14V Input / 1A / PWM Step-Down Converters
MAX1685EEEMAXIM ?N/a35avaiLow-Noise / 14V Input / 1A / PWM Step-Down Converters
MAX1685EEEMAXINN/a47avaiLow-Noise / 14V Input / 1A / PWM Step-Down Converters


MAX1685EEE ,Low-Noise / 14V Input / 1A / PWM Step-Down Convertersapplications thatrequire highest efficiency. The MAX1685 runs at' Small 16-QSOP Package600kHz to al ..
MAX1685EEE ,Low-Noise / 14V Input / 1A / PWM Step-Down ConvertersELECTRICAL CHARACTERISTICS(V = V = +6V, STBY = SYNC/PWM = CVL, V = V , FB = AGND, circuit of Figure ..
MAX1685EEE ,Low-Noise / 14V Input / 1A / PWM Step-Down ConvertersApplicationsINPUT OUTPUTCellular Phones3.3V AT 1A2.7V TO 14V2-Way Radios and Walkie-Talkies IN LX+ ..
MAX1685EEE ,Low-Noise / 14V Input / 1A / PWM Step-Down ConvertersMAX1684/MAX168519-1454; Rev 0; 4/99Low-Noise, 14V Input, 1A, PWM Step-Down Converters
MAX1685EEE+ ,Low-Noise, 14V Input, 1A, PWM Step-Down ConvertersMAX1684/MAX168519-1454; Rev 2; 7/01Low-Noise, 14V Input, 1A, PWM Step-Down Converters
MAX1685EEE+ ,Low-Noise, 14V Input, 1A, PWM Step-Down Convertersapplications, an auxiliary 3V/5mAPART TEMP RANGE PIN-PACKAGEoutput, and a 1% accurate reference. MA ..
MAX4482AKA-T ,Single/Dual/Quad / Low-Cost / Single-Supply / Rail-to-Rail Op Amps with ShutdownELECTRICAL CHARACTERISTICS(V = +5V, V = 0, V = 0, V = V /2, R ≥ 1MΩ connected to V /2, SHDN = V (MA ..
MAX4482ASA+ ,Single/Dual/Quad, Low-Cost, Single-Supply, Rail-to-Rail Op Amps with ShutdownApplicationsMAX4481AUT+T -40°C to +125°C 6 SOT23 AAOS● Single-Supply Zero-Crossing Detectors● Instr ..
MAX4483ASD+T ,Single/Dual/Quad, Low-Cost, Single-Supply, Rail-to-Rail Op Amps with ShutdownElectrical Characteristics (continued)(V = +5V, V = 0V, V = 0V, V = V /2, R ≥ 1MΩ connected to V /2 ..
MAX4483AUD+ ,Single/Dual/Quad, Low-Cost, Single-Supply, Rail-to-Rail Op Amps with ShutdownEVALUATION KIT AVAILABLEMAX4480–MAX4483 Single/Dual/Quad, Low-Cost, Single-Supply, Rail-to-Rail Op ..
MAX4484AUK ,Single/Dual/Quad, Low-Cost, Single-Supply 7MHz, Rail-to-Rail Op AmpsFeaturesThe MAX4484/MAX4486/MAX4487 single/dual/quad low- ● 7MHz Unity-Gain Stable Bandwidthcost ge ..
MAX4484AXK-T ,Single/Dual/Quad / Low-Cost / Single-Supply 7MHz / Rail-to-Rail Op AmpsELECTRICAL CHARACTERISTICS—T = +25°CA(V = +5.0V, V = 0, V = 0, V = V /2, R = ∞ to V /2, unless othe ..


MAX1684EEE-MAX1685EEE
Low-Noise / 14V Input / 1A / PWM Step-Down Converters
General Description
The MAX1684/MAX1685 are high-efficiency, internal-
switch, PWM step-down switching regulators intended to
power cellular phones, communicating PDAs, and
handy-terminals. These devices deliver a guaranteed 1A
output current from two Li-Ion batteries. Their wide input
voltage range of 2.7V to 14V gives design flexibility and
allows batteries to charge from a wall cube, since the ICs
operate at the higher voltages that occur when the bat-
tery is removed. The output voltage is preset to 3.3V or
can be externally adjusted from 1.25V to VIN.
The low-on-resistance power switch and built-in synchro-
nous rectifier provide high efficiencies of up to 96%.
There are four modes of operation: fixed-frequency
mode, normal mode, low-power mode, and shutdown
mode. The fixed-frequency PWM mode of operation
offers excellent noise characteristics. The normal mode
maintains high efficiency at all loads. The low-power
mode is used to conserve power in standby or when full
load is not required. The shutdown mode is used to
power down the device for minimal current draw.
The MAX1684 runs at 300kHz for applications that
require highest efficiency. The MAX1685 runs at
600kHz to allow use of smaller external components.
These devices can also be synchronized to an external
clock. Other features include a 100% duty cycle for
low-dropout applications, an auxiliary 3V/5mA output,
and a 1% accurate reference.
Both devices are available in a space-saving 16-QSOP
package. An evaluation kit is also available to help
speed designs. For a similar device in a 10-pin µMAX
package with lower input voltage requirements (5.5V
max), see the MAX1692 data sheet.
Applications

Cellular Phones
2-Way Radios and Walkie-Talkies
Computer Peripherals
Personal Communicators
PDAs and Handy-Terminals
Features
Up to 96% Efficiency1A Guaranteed Output Current100% Duty Cycle in Dropout 2.7V to 14V Input Range (15V absolute max)±1% Accurate Reference Output 0.24ΩP-Channel On-ResistanceSynchronizable Switching FrequencyFixed-Frequency PWM Operation
300kHz (MAX1684)
600kHz (MAX1685)
150µA Normal Mode Quiescent Current25µA Low-Power Mode Quiescent Current2µA Shutdown CurrentDual Mode™Fixed 3.3V (±1%) Output or
Adjustable Output (1.25V to VIN)
Small 16-QSOP PackageAuxiliary Output (CVL): 3V/5mA
MAX1684/MAX1685
Low-Noise, 14V Input, 1A, PWM
Step-Down Converters
Typical Operating Circuit
Ordering Information
Pin Configuration appears at end of data sheet.
MAX1684/MAX1685
Low-Noise, 14V Input, 1A, PWM
Step-Down Converters
ABSOLUTE MAXIMUM RATINGS
ELECTRICAL CHARACTERISTICS

(VIN= VSHDN= +6V, STBY= SYNC/PWM = CVL, VBOOT= VOUT, FB = AGND, circuit of Figure 1, TA= 0°C to +85°C,unless other-
wise 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.
AIN to AGND............................................................-0.3 to +15V
IN to PGND................................................-0.3V to (VAIN+ 0.3V)
LX to PGND.................................................-0.5V to (VIN+ 0.3V)
PGND to AGND..................................................................±0.3VSHDNto AGND.........................................-0.3V to (VAIN+ 0.3V)
ILIM/SS, FB, CC, BOOT, REF to AGND.....-0.3V to (VCVL+ 0.3V)
CVH to IN..................................................................-6V to +0.3V
CVL, STBY, SYNC/PWM to AGND............................-0.3V to +6V
Reference Current..............................................................±1mA
CVL Current ..........................................................10mA to -1mA
LX Peak Current (Internally Limited).....................................2.3A
Continuous Power Dissipation (TA= +70°C)
16-Pin QSOP (derate 8.3mW/°C above +70°C)............667mW
Operating Temperature Range...........................-40°C to +85°C
Junction Temperature......................................................+150°C
Storage Temperature Range.............................-65°C to +150°C
Lead Temperature (soldering, 10sec )............................+300°C
MAX1684/MAX1685
Low-Noise, 14V Input, 1A, PWM
Step-Down Converters
ELECTRICAL CHARACTERISTICS (continued)

(VIN= VSHDN= +6V, STBY= SYNC/PWM = CVL, VBOOT= VOUT, FB = AGND, circuit of Figure 1, TA= 0°C to +85°C,unless other-
wise noted. Typical values are at TA= +25°C.)
MAX1684/MAX1685
Low-Noise, 14V Input, 1A, PWM
Step-Down Converters
ELECTRICAL CHARACTERISTICS

(VIN= VSHDN= +6V, STBY= SYNC/PWM = CVL, VBOOT= VOUT, FB = AGND, circuit of Figure 1, TA= -40°C to +85°C, unless other-
wise noted.) (Note 5)
Note 1:
The output adjust range with BOOT connected to VOUTis VREFto 5.5V. Connect BOOT to AGND for VOUT> 5.5V.
Note 2:
The quiescent power-consumption specifications include chip supply and gate-drive loss only. Divide these values by VIN
(= 6V) to obtain quiescent currents. In normal and low-power modes, chip supply current dominates and quiescent power
is proportional to VBOOT(BOOT connected to OUT). In PWM mode, gate-drive loss dominates and quiescent power is pro-
portional to VIN·(VIN- VCVH). In addition, IR losses in power switches and external components typically increase PWM
quiescent power consumption by 5mW to 10mW. Note that if the device is not bootstrapped, additional power will be dissi-
pated in the CVL linear regulator.
Note 3:
When the duty factor (VOUT/ VIN) is less than this value, the switching frequency decreases in PWM mode to maintain regu-
lation.
Note 4:
Thermal shutdown is disabled in low-power mode (STBY= low) to reduce power consumption.
Note 5:
Specifications to -40°C are guaranteed by design, not production tested.
MAX1684/MAX1685
Low-Noise, 14V Input, 1A, PWM
Step-Down Converters
Typical Operating Characteristics

(Circuit of Figure 1, TA = +25°C, unless otherwise noted.)
MAX1684/MAX1685
Low-Noise, 14V Input, 1A, PWM
Step-Down Converters ypical Operating Characteristics (continued)

(Circuit of Figure 1, TA = +25°C, unless otherwise noted.)
MAX1684/MAX1685
Low-Noise, 14V Input, 1A, PWM
Step-Down Converters
Pin Descriptionypical Operating Characteristics (continued)

(Circuit of Figure 1, TA = +25°C, unless otherwise noted.)
MAX1684/MAX1685
Low-Noise, 14V Input, 1A, PWM
Step-Down Converters
_______________Detailed Description

The MAX1684/MAX1685 step-down, pulse-width-modu-
lation (PWM) DC-DC converters provide an adjustable
output from 1.25V to the input voltage. They accept
inputs from 2.7V to 14V and deliver up to 1.6A. An inter-
nal MOSFET and synchronous rectifier reduce PC
board area while maintaining high efficiency. Operation
with up to 100% duty cycle minimizes dropout voltage.
Fixed-frequency PWM operation reduces interference
in sensitive communications and data-acquisition appli-
cations. A SYNC input allows synchronization to an
external clock. The MAX1684/MAX1685 can operate in
five modes. Setting the devices to operate in the appro-
priate mode for the intended application (Table 1)
achieves highest efficiency.
PWM Control

The MAX1684/MAX1685 use an oscillator-triggered min-
imum/maximum on-time current-mode control scheme
(Figure 2). The minimum on-time is typically 220ns
unless the regulator is in dropout. The maximum on-time
is 2 / fOSC, allowing operation to 100% duty cycle.
Current-mode feedback provides cycle-by-cycle current
limiting for superior load- and line-transient response.
At each falling edge of the internal oscillator, the inter-
nal P-channel MOSFET (main switch) turns on. This
allows current to ramp up through the inductor to the
load and stores energy in a magnetic field. The switch
remains on until either the current-limit comparator
trips, the maximum on-time expires, or the PWM com-
parator signals that the output is in regulation. When
the switch turns off during the second half of each
cycle, the inductor’s magnetic field collapses, releasing
the stored energy and forcing current through the out-
put diode to the output filter capacitor and load. The
output filter capacitor stores charge when the inductor
current is high and releases it when the inductor cur-
rent is low, smoothing the voltage across the load.
During normal operation, the MAX1684/MAX1685 regu-
late the output voltage by switching at a constant fre-
quency and modulating the power transferred to the
load on each cycle using the PWM comparator. A multi-
input comparator sums three weighted differential sig-
nals (the output voltage with respect to the reference,
the main switch current sense, and the slope-compen-
sation ramp) and changes states when a threshold is
reached. It modulates output power by adjusting the
Table 1. Operating Modes
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