Document
19-1290; Rev 1; 2/98
Regulated, Adjustable -2x Inverting Charge Pump MAX868
General Description
The MAX868 inverting charge pump provides a low-cost and compact means of generating a regulated negative voltage up to -2 x V IN from a positive input voltage between 1.8V and 5.5V. It uses a pulse-frequencymodulation (PFM) control scheme to generate the regulated negative output voltage. PFM operation is obtained by gating the internal 450kHz oscillator on and off as needed to maintain output voltage regulation. This unique on-demand switching scheme gives the MAX868 excellent light-load efficiency without degrading its fullload operation (up to 30mA), permitting smaller capacitors to take advantage of the oscillator’s high switching frequency. The MAX868 requires no inductors; only four capacitors are required to build a complete DC-DC converter. Output voltage regulation is achieved by adding just two resistors. The MAX868 comes in a 10-pin µMAX package, which is only 1.11mm high and occupies just half the board area of a standard 8-pin SO.
____________________________Features
o Regulated Negative Output Voltage (up to -2 x VIN) o Ultra-Small, 10-Pin µMAX Package o On-Demand Switching at up to 450kHz o 30µA Quiescent Supply Current o Requires Only Four Small External Capacitors o 1.8V to 5.5V Input Voltage Range o 0.1µA Logic-Controlled Shutdown o Up to 30mA Output Current
Ordering Information
PART TEMP. RANGE PIN-PACKAGE Dice* 10 µMAX MAX868C/D 0°C to +70°C MAX868EUB -40°C to +85°C *Dice are tested at TA = +25°C.
________________________Applications
Small LCD Panels Cell Phones Cordless Phones Camcorders Handy-Terminals, PDAs Medical Instruments Battery-Operated Equipment
Typical Operating Circuit Configuration
VIN = 1.8V TO 5.5V 1µF
TOP VIEW
SHDN
IN
MAX868
GND 1 OUT C1PGND C1+ 2 3 4 5 10 FB 9 SHDN C2+ IN C2C2+ 0.1µF C2PGND GND OUT 2.2µF C1+ 0.1µF C1VOUT = 0V TO -2 x VIN FB
MAX868
8 7 6
µMAX
________________________________________________________________ Maxim Integrated Products
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Regulated, Adjustable -2x Inverting Charge Pump MAX868
ABSOLUTE MAXIMUM RATINGS
IN to GND .................................................................-0.3V to +6V OUT to GND ...........................................................+0.3V to -12V IN to OUT.................................................................-0.3V to -17V C1+ to GND ........................................(VIN - 12V) to (VIN + 0.3V) C1- to GND.............................................................+0.3V to -12V C2+ to GND ....................................................(VIN + 0.3V) to -6V C2- to GND...............................................................+0.3V to -6V SHDN, FB to GND .......................................-0.3V to (VIN + 0.3V) PGND to GND .......................................................-0.3V to +0.3V Output Current ....................................................................35mA Short-Circuit Duration.................................................Continuous Continuous Power Dissipation (TA = +70°C) 10-pin µMAX (derate 5.6mW/°C above +70°C) ...........444mW Operating Temperature Range MAX868EUB ....................................................-40°C to +85°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
(VIN = +3.3V, SHDN = IN, C1 = C2 = 0.22µF, CIN = 1µF, COUT = 10µF, TA = 0°C to +85°C, unless otherwise noted. Typical values are at TA = +25°C.) PARAMETER Supply-Voltage Range Supply Current Shutdown Current Oscillator Frequency Closed-Loop Output Resistance Open-Loop Output Resistance FB Trip Point Output Current FB Input Bias Current SHDN Input Threshold SHDN Input Bias Current VIL VIH IOUT SYMBOL VIN IIN IIN,SHDN fOSC ROUT,CL RL = 3kΩ to GND No load, VFB = -50mV FB = IN No load, SHDN = GND VFB = 50mV VOUT = -5V IOUT = 5mA, FB = IN TA = +25°C TA = 0°C to +85°C 15 -30 -40 12 30 -50 0.3VIN 0.7VIN -100 1 100 1 50 TA = +25°C TA = 0°C to +85°C VIN = 3.3V, VOUT = -5V VIN = 5V, VOUT = -3.3V TA = +25°C TA = 0°C to +85°C 293 270 0.2 70 100 125 50 30 40 mV mV mA nA V nA Ω CONDITIONS MIN 1.8 30 5 0.1 450 1 607 630 TYP MAX 5.5 50 UNITS V µA mA µA kHz Ω
ROUT
SHDN = GND (OUT pulls to GND) VIN = 1.8V to 5.5V Closed loop
VIN = 1.8V to 5.5V, TA = +25°C VIN = 1.8V to 5.5V VIN = 5.5V, SHDN = IN or GND
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