General Description The MAX1684 MAX1685 are high efficiency internal switch pulse width modulation PWM step down switch ing regulators intended to power cellular phones communicating PDAs and handy terminals These devices deliver a guaranteed 1A output current from two lithium ion Li+ batteries Their wide input voltage range of 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 battery is removed The output voltage is preset to 3V or can be externally adjusted from 25V to VIN The low on resistance power switch and built in synchro nous rectifier provide high efficiencies of up to There are four modes of operation: fixed frequency nor mal low power and shutdown The fixed frequency PWM mode of operation offers excellent noise character istics 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 cur rent draw The MAX1684 runs at 300kHz for applications that require highest efficiency The MAX1685 runs at 600kHz to allow the use of smaller external compo nents These devices can also be synchronized to an external clock Other features include a duty cycle for low dropout applications an auxiliary 3V 5mA output and a accurate reference Both devices are available in a space saving QSOP package An evaluation kit is also available to help speed designs For a similar device in a pin MAX package with lower input voltage requirements 5V max refer to the MAX1692 data sheet

Fe Campillo

Description

Niveau: Supérieur, Doctorat, Bac+8
General Description The MAX1684/MAX1685 are high-efficiency, internal- switch, pulse-width modulation (PWM) step-down switch- ing regulators intended to power cellular phones, communicating PDAs, and handy-terminals. These devices deliver a guaranteed 1A output current from two lithium-ion (Li+) 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 battery 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, nor- mal, low-power, and shutdown. The fixed-frequency PWM mode of operation offers excellent noise character- istics. 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 cur- rent draw. The MAX1684 runs at 300kHz for applications that require highest efficiency. The MAX1685 runs at 600kHz to allow the use of smaller external compo- nents.

• load current


• low


• khz


• logic input


• output voltage


• µa


• max1685


• foscoscillator frequency


• pwm

Sujets

• Extremum

Informations

• Publié par: profil-zyak-2012
• Nombre de lectures: 6
• Langue: English

Extrait

MAX1684/MAX1685
19-1454; Rev 2; 7/01
Low-Noise, 14V Input, 1A, PWM
Step-Down Converters
General Description Features
The MAX1684/MAX1685 are high-efficiency, internal- Up to 96% Efficiency
switch, pulse-width modulation (PWM) step-down switch-
1A Guaranteed Output Currenting regulators intended to power cellular phones,
communicating PDAs, and handy-terminals. These 100% Duty Cycle in Dropout
devices deliver a guaranteed 1A output current from two
2.7V to 14V Input Range (15V Absolute Max)lithium-ion (Li+) batteries. Their wide-input voltage range
of 2.7V to 14V gives design flexibility and allows batteries ±1% Accurate Reference Output
to charge from a wall cube, since the ICs operate at the
0.24Ω P-Channel On-Resistancehigher voltages that occur when the battery is removed.
The output voltage is preset to 3.3V or can be externally Synchronizable Switching Frequency
adjusted from 1.25V to V .IN
Fixed-Frequency PWM Operation
The low on-resistance power switch and built-in synchro-
300kHz (MAX1684) nous rectifier provide high efficiencies of up to 96%.
600kHz (MAX1685)There are four modes of operation: fixed-frequency, nor-
mal, low-power, and shutdown. The fixed-frequency 150µA Normal-Mode Quiescent Current
PWM mode of operation offers excellent noise character-
25µA Low-Power Mode Quiescent Currentistics. The normal mode maintains high efficiency at all
loads. The low-power mode is used to conserve power in 2µA Shutdown Current
standby or when full load is not required. The shutdown
Dual Mode™ Fixed 3.3V (±1%) Output or mode is used to power down the device for minimal cur-
Adjustable Output (1.25V to V )rent draw. IN
The MAX1684 runs at 300kHz for applications that Small 16-QSOP Package
require highest efficiency. The MAX1685 runs at
Auxiliary Output (CVL): 3V/5mA
600kHz to allow the use of smaller external compo-
nents. These devices can also be synchronized to an
Ordering Informationexternal clock. Other features include a 100% duty
cycle for low-dropout applications, an auxiliary 3V/5mA PART TEMP RANGE PIN-PACKAGE
output, and a 1% accurate reference.
MAX1684EEE -40°C to +85°C 16 QSOP
Both devices are available in a space-saving 16-QSOP MAX1685EEE
package. An evaluation kit is also available to help
speed designs. For a similar device in a 10-pin µMAX
Typical Operating Circuitpackage with lower input voltage requirements (5.5V
max), refer to the MAX1692 data sheet.
Applications
OUTPUTINPUT
2.7V TO 14V 3.3V AT 1ACellular Phones
IN LX ++
Two-Way Radios and Walkie-Talkies
AIN MAX1684
Computer Peripherals MAX1685SHDN
GND
Personal Communicators
CVHPDAs and Handy-Terminals
CVL BOOT
STBY
SYNC/PWM
Pin Configuration appears at end of data sheet. FB CC REF
Dual Mode is a trademark of Maxim Integrated Products, Inc.
________________________________________________________________ Maxim Integrated Products 1
For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct! at
1-888-629-4642, or visit Maxim’s website at www.maxim-ic.com.
EVALUATION KIT
AVAILABLELow-Noise, 14V Input, 1A, PWM
Step-Down Converters
ABSOLUTE MAXIMUM RATINGS
AIN to AGND ............................................................-0.3 to +15V CVL Current .......................................................-1mA to +10mA
IN to PGND ................................................-0.3V to (V + 0.3V) LX Peak Current (Internally Limited) .....................................2.3AAIN
LX to PGND .................................................-0.5V to (V Continuous Power Dissipation (T = +70°C)IN A
PGND to AGND ..................................................................±0.3V 16-Pin QSOP (derate 8.3mW/°C above +70°C)............667mW
SHDN to AGND .........................................-0.3V to (V + 0.3V) Operating Temperature Range ...........................-40°C to +85°CAIN
ILIM/SS, FB, CC, BOOT, REF to AGND ....-0.3V to (V Junction Temperature......................................................+150°CCVL
CVH to IN..................................................................-6V to +0.3V Storage Temperature Range .............................-65°C to +150°C
CVL, STBY, SYNC/PWM to AGND............................-0.3V to +6V Lead Temperature (soldering, 10s) .................................+300°C
Reference Current ..............................................................±1mA
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.
ELECTRICAL CHARACTERISTICS
(V = V = 6V, STBY = SYNC/PWM = CVL, V = V , FB = AGND, circuit of Figure 1, T = 0°C to +85°C, unless otherwiseIN SHDN BOOT OUT A
noted. Typical values are at T = +25°C.)A
PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS
Input Voltage Range 2.7 14 V
Feedback Voltage V V = V , I = 0 to 1A 1.238 1.251 1.264 VFB FB OUT LOAD
Output Voltage (3.3V Mode) V FB = AGND, I 3.296 3.333 3.368 VOUT LOAD
Output Load Regulation V = V , I = 0 to 1A 0.01 %FB OUT LOAD
Output Current Capability V = 5V to 14V 1 AIN
Output Adjust Range BOOT = AGND (Note 1) V V VREF IN
FB Input Current I V = 1.4V -50 50 nAFB FB
V = 6V 0.24 0.5INHigh-side switch,
On-Resistance, P-Channel Ω
I = 1ALX V = 2.7V 0.34 0.8IN
On-Resistance, N-Channel Low-side switch, V = 2.7V, I = 200mA 38 ΩIN LX
Current Limit in PWM Mode I 1.2 1.75 2.3 ALIM
Pulse-Skipping Current Threshold SYNC/PWM = low 285 380 475 mA
Current Limit in Low-Power
I STBY = low 285 380 475 mALIMLPMode
Current Limit, N-Channel SYNC/PWM = high 0.15 0.4 0.9 A
MAX1684 -10 50 100
Zero Crossing Threshold SYNC/PWM = low mA
MAX1685 20 80 130
PWM mode, MAX1684 13 33
SYNC/PWM = high,
V = 3.3V BOOT
MAX1685 25 65(Note 2)
Quiescent Power Consumption mW
Normal mode, SYNC/PWM = low,
0.9 2
V = 3.3V (Note 2)BOOT
Low-power mode, STBY = low,
0.14 0.27
VBOOT
2 _______________________________________________________________________________________
MAX1684/MAX1685MAX1684/MAX1685
Low-Noise, 14V Input, 1A, PWM
Step-Down Converters
ELECTRICAL CHARACTERISTICS (continued)
(V = V = 6V, STBY = SYNC/PWM = CVL, V = V , FB = AGND, circuit of Figure 1, T = 0°C to +85°C, unless otherwiseIN SHDN BOOT OUT A
noted. Typical values are at T = +25°C.)A
PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS
Quiescent Supply Current
STBY = low, V = 2.7V 230 430 µAINin Dropout
Shutdown Supply Current SHDN = low 26 µA
LX Leakage Current I V = 14V, V = 0 or 14V, SHDN = low 20 µALX IN LX
MAX1684 260 300 340
Oscillator Frequency f kHzOSC
MAX1685 520 600 680
MAX1684 180 350
SYNC Capture Range kHz
MAX1685 360 700
Maximum Duty Cycle 100 %
MAX1684 10Constant-Frequency Minimum
(Note 3) %
Duty Cycle MAX1685 20
Reference Output Voltage V I = 0 1.238 1.251 1.264 VREF REF
Reference Load Regulation -1µA < I < 50µA 415 mVREF
Reference Supply Regulation 2.7V < V < 5.5V 0.2 5 mVBOOT
V = 3V to 14V, BOOT = AGND,INCVL Regulator Output Voltage 2.7 3.0 3.15 V
I = 0 to 5mACVL
CVL Dropout Voltage BOOT = AGND, I = 5mA 120 mVCVL
CVL Undervoltage Lockout BOOT = AGND, CVL falling edge,
2.35 2.5 2.6 V
Threshold typical hysteresis is 40mV
CVH with Respect to V I = -1mA -5.0 -4.6 -4.1 VIN CVH
BOOT falling edge,
BOOT Switchover Threshold 2.35 2.5 2.65 V
typical hysteresis is 0.1V
Thermal Shutdown Threshold Typical hysteresis is +10°C (Note 4) 160 °C
ILIM/SS Source Current V = 1.4V 3.3 4 4.65 µAILIM/SS
Logic Input High Voltage V 2 VIH
SHDN, STBY, SYNC/PWM
Logic Input Low Voltage V 0.7 VIL
Logic Input Current -1 1 µASHDN, STBY
SYNC/PWM Pulse Width High or low period 500 ns
_______________________________________________________________________________________ 3Low-Noise, 14V Input, 1A, PWM
Step-Down Converters
ELECTRICAL CHARACTERISTICS
(V = V = 6V, STBY = SYNC/PWM = CVL, V = V , FB = AGND, circuit of Figure 1, T = -40°C to +85°C, unless other-IN SHDN BOOT OUT A
wise noted.) (Note 5)
PARAMETER SYMBOL CONDITIONS MIN MAX UNITS
Input Voltage Range 2.7 14 V
Output Feedback Voltage V V = V , I = 0 to 1A 1.233 1.269 VFB FB OUT LOAD
Output Voltage (3.3V Mode) V FB = AGND, I 3.280 3.382 VOUT LOAD
Output Current Capability V = 6V to 14V 1 AIN
Output Adjust Range BOOT = AGND (Note 1) V V VREF IN
FB Input Current I V = 1.4V -50 50 nAFB FB
Current Limit in PWM Mode I 1.2 2.3 ALIM
Current Limit in Low-Power
I STBY = low 285 475 mALIMLPMode
Normal mode, SYNC/PWM = low,
2
V = 3.3V (Note 2)BOOT
Quiescent Power Consumption mW
Low-power mode, STBY = low,
0.27
VBOOT
Shutdown Supply Current 6 µASHDN = low
MAX1684 240 350
Oscillator Frequency f kHzOSC
MAX1685 480 700
Reference Output Voltage I = 0 1.232 1.268 VREF
V = 3V to 14V, BOOT = AGND, INCVL Regulator Output Voltage 2