Document
19-1198; Rev 0; 4/97
1- to 3-Cell, High-Current, Low-Noise, Step-Up DC-DC Converters with Linear Regulator
_______________General Description
The MAX1705/MAX1706 are high-efficiency, low-noise, step-up DC-DC converters with an auxiliary linearregulator output. These devices are intended for use in battery-powered wireless applications. They use a synchronous rectifier pulse-width-modulation (PWM) boost topology to generate 2.5V to 5.5V outputs from battery inputs, such as 1 to 3 NiCd/NiMH cells or 1 Li-Ion cell. The MAX1705 has an internal 1A N-channel MOSFET switch. The MAX1706 has a 0.5A switch. Both devices also have a built-in low-dropout linear regulator that delivers up to 200mA. With an internal synchronous rectifier, the MAX1705/ MAX1706 deliver 5% better efficiency than similar nonsynchronous converters. They also feature a pulsefrequency-modulation (PFM) standby mode to improve efficiency at light loads, and a 1µA shutdown mode. An efficiency-enhancing track mode reduces the step-up DC-DC converter output to 300mV above the linear-regulator output. Both devices come in a 16-pin QSOP package, which occupies the same space as an 8-pin SO. Other features include two shutdown-control inputs for push-on/push-off control, and an uncommitted comparator for use as a voltage monitor.
ANUAL N KIT M IO T A U EVAL BLE AVAILA
____________________________Features
o Up to 96% Efficiency o 1.1VIN Guaranteed Start-Up o Up to 850mA Output (MAX1705) o Step-Up Output (2.5V to 5.5V adjustable) o Linear Regulator (1.25V to 5.0V adjustable) o PWM/PFM Synchronous-Rectified Topology o 300kHz PWM Mode or Synchronizable o 1µA Shutdown Mode o Voltage Monitor o Pushbutton On/Off Control
MAX1705/MAX1706
______________Ordering Information
PART MAX1705C/D TEMP. RANGE 0°C to +70°C PIN-PACKAGE Dice*
16 QSOP -40°C to +85°C MAX1705EEE Dice* MAX1706C/D 0°C to +70°C 16 QSOP MAX1706EEE -40°C to +85°C *Dice are tested at TA = +25°C, DC parameters only.
________________________Applications
Digital Cordless Phones Personal Communicators Palmtop Computers Hand-Held Instruments PCS Phones Wireless Handsets Two-Way Pagers
__________Typical Operating Circuit
INPUT 0.7V TO 5.5V
__________________Pin Configuration
LOW-BATTERY DETECTION
LX LBP POUT OUT
STEP-UP OUTPUT
TOP VIEW
LBP 1 LBN 2 REF 3 TRACK 4 GND 5 OUT 6 FB 7 FBLDO 8
16 POUT
LBO
15 ONA 14 ONB
MAX1705 MAX1706
FB
ON/OFF CONTROL HIGH EFFICIENCY LOW NOISE
ONA ONB CLK/SEL TRACK LBN REF LDO FBLDO GND PGND LINEAR REGULATOR OUTPUT
MAX1705 MAX1706
13 LX 12 PGND 11 CLK/SEL 10 LBO 9 LDO
QSOP
________________________________________________________________ Maxim Integrated Products
1
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1- to 3-Cell, High-Current, Low-Noise, Step-Up DC-DC Converters with Linear Regulator MAX1705/MAX1706
ABSOLUTE MAXIMUM RATINGS
ONA, ONB, FBLDO, OUT, POUT to GND...................-0.3V to 6V PGND to GND.....................................................................±0.3V POUT to OUT ......................................................................±0.3V LX to PGND ............................................-0.3V to (VPOUT + 0.3V) CLK/SEL, REF, FB, TRACK, LDO, LBN, LBP, LBO to GND.......................-0.3V to (VOUT + 0.3V) LDO Short Circuit .......................................................Continuous Continuous Power Dissipation (TA = +70°C) QSOP (derate 8.70mW/°C above +70°C) ...................696mW Operating Temperature Range ...........................-40°C to +85°C Junction Temperature ......................................................+150°C Storage Temperature Range .............................-65°C to +160°C Lead Temperature (soldering, 10sec) .............................+300°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.
ELECTRICAL CHARACTERISTICS
(VOUT = VPOUT = VLBP = 3.6V, CLK/SEL = FB = LBN = LBO = ONA = ONB = TRACK = GND, REF = open (bypassed with 0.22µF), LX = open, TA = 0°C to +85°C, unless otherwise noted. Typical values are at TA = +25°C.) PARAMETER DC-DC CONVERTER Minimum Start-Up Voltage Minimum Operating Battery Voltage FB Regulation Voltage FB Input Current OUT Adjust Range Load Regulation MAX1705, 0A ≤ ILX ≤ 0.5A; MAX1706, 0A ≤ ILX ≤ 0.25A; CLK/SEL = OUT TRACK = VLDO > 2.3V fLX VPOUT = VOUT = 1.5V (Note 2) IOUT IOUT ONA = GND, ONB = OUT, measure IOUT CLK/SEL = GND, VFB = VFBLDO = 1.5V, no load VFB = VFBLDO = 1.5V, no load IOUT CLK/SEL = OUT FB = GND (LX switching) IREF = 0µA -1µA < IREF < 50µA 2.5V < VOUT < 5.5V 1.238 2.1 1.250 4 0.2 1.262 15 5 mA V mV mV VLDO + 0.2 40 2.00 TA = +25°C, ILOAD < 1mA, Figure 2 (Note 1).