Document
19-3336; Rev 0; 7/04
KIT ATION EVALU E L B AVAILA
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16µA IQ, 1.2A PWM Step-Down DC-DC Converters
General Description Features
♦ Up to 97% Efficiency ♦ 95% Efficiency at 1mA Load Current ♦ Low 16µA Quiescent Current ♦ 1MHz PWM Switching ♦ Tiny 3.3µH Inductor ♦ Selectable 3.3V, 2.5V, 1.8V, 1.5V, 1.3V, 1.0V, and Adjustable Output ♦ 1.2A Guaranteed Output Current (MAX1556) ♦ Voltage Positioning Optimizes Load-Transient Response ♦ Low 27µA Quiescent Current in Dropout ♦ Low 0.1µA Shutdown Current ♦ No External Schottky Diode Required ♦ Analog Soft-Start with Zero Overshoot Current ♦ Small, 10-Pin, 3mm x 3mm TDFN Package
MAX1556/MAX1557
The MAX1556/MAX1557 are low-operating-current (16µA), fixed-frequency step-down regulators. High efficiency, low-quiescent operating current, low dropout, and minimal (27µA) quiescent current in dropout make these converters ideal for powering portable devices from 1-cell Li-ion or 3-cell alkaline/NiMH batteries. The MAX1556 delivers up to 1.2A; has pin-selectable 1.8V, 2.5V, and 3.3V outputs; and is also adjustable. The MAX1557 delivers up to 600mA; has pin-selectable 1V, 1.3V, and 1.5V outputs; and is also adjustable. The MAX1556/MAX1557 contain a low-on-resistance internal MOSFET switch and synchronous rectifier to maximize efficiency and dropout performance while minimizing external component count. A proprietary topology offers the benefits of a high fixed-frequency operation while still providing excellent efficiency at both light and full loads. A 1MHz PWM switching frequency keeps components small. Both devices also feature an adjustable soft-start to minimize battery transient loading. The MAX1556/MAX1557 are available in a tiny 10-pin TDFN (3mm x 3mm) package.
Applications
PDAs and Palmtop Computers Cell Phones and Smart Phones Digital Cameras and Camcorders Portable MP3 and DVD Players Hand-Held Instruments
MAX1557ETB MAX1556ETB PART
Ordering Information
TEMP RANGE -40°C to +85°C -40°C to +85°C PIN-PACKAGE 10 TDFN-EP* (T1033-1) 10 TDFN-EP* (T1033-1) TOP MARK ACQ ACR
*EP = Exposed paddle.
Typical Operating Circuit
INPUT 2.6V TO 5.5V OUTPUT 0.75V TO VIN INP LX
TOP VIEW
Pin Configuration
MAX1556/ MAX1557
PGND IN VOLTAGE SELECT ON OFF SHDN GND D1 D2 SS OUT
IN
GND SS OUT SHDN
1 2 3 4 5
TDFN
10 9
D1
INP LX
MAX1556/ MAX1557
8 7 6
PGND D2
________________________________________________________________ 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.
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16µA IQ, 1.2A PWM DC-DC Step-Down Converters MAX1556/MAX1557
ABSOLUTE MAXIMUM RATINGS
IN, INP, OUT, D2, SHDN to GND ..........................-0.3V to +6.0V SS, D1 to GND .............................................-0.3V to (VIN + 0.3V) PGND to GND .......................................................-0.3V to +0.3V LX Current (Note 1)...........................................................±2.25A Output Short-Circuit Duration.....................................Continuous Continuous Power Dissipation (TA = +70°C) 10-Pin TDFN (derate 24.4mW/°C above +70°C) .......1951mW Operating Temperature Range ...........................-40°C to +85°C Junction Temperature ......................................................+150°C Storage Temperature Range .............................-65°C to +150°C Lead Temperature (soldering, 10s) .................................+300°C
Note 1: LX has internal clamp diodes to GND and IN. Applications that forward bias these diodes should take care not to exceed the IC’s package power-dissipation limits.
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
(VIN = VINP = VSHDN = 3.6V, TA = - 40°C to +85°C. Typical values are at TA = +25°C, unless otherwise noted.) (Note 1)
PARAMETER Input Voltage Undervoltage-Lockout Threshold Quiescent Supply Current Shutdown Supply Current Output Voltage Range No load TA = 0°C to +85°C (Note 2) Output Accuracy TA = -40°C to +85°C (Note 2) MAX1556 MAX1557 D1 = D2 = GND TA = +25°C TA = +85°C No load 300mA load 600mA load 1200mA load, MAX1556 only No load 300mA load 600mA load 1200mA load, MAX1556 only -0.50 -1.2 -1.75 -3.25 -1.25 -1.75 -2.75 -4.25 300mA load 600mA load 1200mA load, MAX1556 only No load 300mA load 600mA load 1200mA load, MAX1556 only Maximum Output Current VIN rising and falling, 35mV hysteresis (typ) No switching, D1 = D2 = GND Dropout SHDN = GND TA = +25°C TA = +85°C 0.75 -0.25 -0.75 -1.5 -2.75 -0.75 -1.5 -2.25 -4.0 1200 600 0.01 0.01 3 +0.75 0 -0.75 -2.25 4.5 +1.75 +1.2 +0.25 -1.25 +2.25 +1.50 +0.25 -1..