Datasheet

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_______________General Description

The MAX864 CMOS, charge-pump, DC-DC voltage

converter produces a positive and a negative output

from a single positive input, and requires only four

capacitors. The charge pump first doubles the input

voltage, then inverts the doubled voltage. The input

voltage ranges from +1.75V to +6.0V.

The internal oscillator can be pin-programmed from

7kHz to 185kHz, allowing the quiescent current, capac-

itor size, and switching frequency to be optimized. The

55Ω output impedance permits useful output currents

up to 20mA. The MAX864 also has a 1µA logic-con-

trolled shutdown.

The MAX864 comes in a 16-pin QSOP package that

uses the same board area as a standard 8-pin SOIC.

For more space-sensitive applications, the MAX865 is

available in an 8-pin µMAX package, which uses half

the board area of the MAX864.

________________________Applications

Low-Voltage GaAsFET Bias in Wireless Handsets

VCO and GaAsFET Supply

Split Supply from 2 to 4 Ni Cells or 1 Li+ Cell

Low-Cost Split Supply for Low-Voltage

Data-Acquisition Systems

Split Supply for Analog Circuitry

LCD Panels

____________________________Features

♦ Requires Only Four Capacitors

♦ Dual Outputs (Positive and Negative)

♦ Low Input Voltages: +1.75V to +6.0V

♦ 1µA Logic-Controlled Shutdown

♦ Selectable Frequencies Allow Optimization

of Capacitor Size and Supply Current

MAX864

Dual-Output Charge Pump with Shutdown

________________________________________________________________

Maxim Integrated Products

MAX864

C1+

V+

V-

SHDNFC1 GNDFC0

C1-

C2+

C2-

+2V

IN

(+1.75V TO +6.0V)

-2V

__________________Pin Configuration

C1+

V+

N.C.



N.C.

IN

GND

N.C.

N.C.

C1-

C2+

GND

C2-

V-

SHDN

FC1

FC0

TOP VIEW

MAX864

QSOP

__________Typical Operating Circuit

19-0478; Rev 0; 3/96

PART

MAX864C/D

MAX864EEE -40°C to +85°C

0°C to +70°C

TEMP. RANGE PIN-PACKAGE

Dice*

16 QSOP

______________Ordering Information

For free samples & the latest literature: http://www.maxim-ic.com, or phone 1-800-998-8800

Contact factory for dice specifications.

Summary of content (12 pages)

PAGE 1
9-0478; Rev 0; 3/96 Dual-Output Charge Pump with Shutdown The MAX864 CMOS, charge-pump, DC-DC voltage converter produces a positive and a negative output from a single positive input, and requires only four capacitors. The charge pump first doubles the input voltage, then inverts the doubled voltage. The input voltage ranges from +1.75V to +6.0V. The internal oscillator can be pin-programmed from 7kHz to 185kHz, allowing the quiescent current, capacitor size, and switching frequency to be optimized.
PAGE 2
MAX864 Dual-Output Charge Pump with Shutdown ABSOLUTE MAXIMUM RATINGS V+ to GND ..............................................................-0.3V to +12V SHDN, FC0, FC1 to GND .............................-0.3V to (V+ + 0.3V) IN to GND ..............................................................-0.3V to +6.2V V- to GND ...............................................................+0.3V to -12V V- Output Current .............................................................
PAGE 3
Dual-Output Charge Pump with Shutdown EFFICIENCY vs. OUTPUT CURRENT @ 33kHz PUMP FREQUENCY V+ 70 V- VIN = 3.3V V- 50 40 30 C1–C4 = 33µF FC1 = 0, FC0 = 0 20 50 40 30 C1–C4 = 6.8µF FC1 = 0, FC0 = 1 0 20 15 25 35 30 5 10 15 20 25 30 OUTPUT CURRENT (mA) OUTPUT CURRENT (mA) EFFICIENCY vs. OUTPUT CURRENT @ 185kHz PUMP FREQUENCY OUTPUT RESISTANCE vs. SUPPLY VOLTAGE V+ V+ 70 60 VIN = 5.
PAGE 4
____________________________Typical Operating Characteristics (continued) (VIN = 5.0V, capacitor values in Table 1, TA = +25°C, unless otherwise noted.) OUTPUT VOLTAGE RIPPLE vs. PUMP CAPACITANCE (VIN = 1.9V, V+ + V- = 6V) 10 100kHz 185kHz 8 7kHz 6 4 2 C1 = C2 = C3 = C4 350 OUTPUT RIPPLE IS MEASURED FOR THE LOAD CURRENT INDICATED IN THE "OUTPUT CURRENT vs. PUMP CAPACITANCE" GRAPH AT VIN = 1.9V.
PAGE 5
Dual-Output Charge Pump with Shutdown MAX864-19 TIME TO EXIT SHUTDOWN +5V 0V FC0 = FC1 = IN (185kHz), C1–C4 = 1µF +10V FC0 = FC1 = GND (7kHz), C1–C4 = 33µF 0V -10V 1ms/div _____________________Pin Description PIN NAME FUNCTION 1 C1- Negative Terminal of the Flying Boost Capacitor 2 C2+ Positive Terminal of the Flying Inverting Capacitor 3, 11 GND Ground (connect pins 3 and 11 together) 4 C2- 5 V- Output of the Inverting Charge Pump SHDN Active-Low Shutdown Input.
PAGE 6
MAX864 Dual-Output Charge Pump with Shutdown _______________Detailed Description Charge-Pump Frequency and Capacitor Selection The MAX864 requires only four external capacitors to implement a voltage doubler/inverter. These may be ceramic or polarized capacitors (electrolytic or tantalum) with values ranging from 0.47µF to 100µF. Figure 2a illustrates the ideal operation of the positive voltage doubler. The on-chip oscillator generates a 50% duty-cycle clock signal.
PAGE 7
Dual-Output Charge Pump with Shutdown Shutdown The MAX864 features a shutdown mode that reduces the maximum supply current to 1µA over temperature. The SHDN pin is an active-low TTL logic-level input. If the shutdown feature is unused, connect SHDN to IN. In shutdown mode, V+ connects to IN through a 22Ω switch and V- connects to GND through a 6Ω switch.
PAGE 8
MAX864 Dual-Output Charge Pump with Shutdown __________Applications Information Positive and Negative Converter The most common application of the MAX864 is as a dual charge-pump voltage converter that provides positive and negative outputs of two times a positive input voltage for biasing analog circuitry (Figure 3). Select a charge-pump frequency high enough so it does not interfere with other circuitry, but low enough to maintain low supply current. See Table 1 for the correct device configuration.
PAGE 9
Dual-Output Charge Pump with Shutdown MAX864 VIN 3.3µF 3.3µF 1 2 3.3µF 3 4 C1- V+ C2+ MAX864 C1+ IN C2V- GND 8 1 7 2 6 5 3.3µF 3 4 C1C2+ MAX864 C2V- V+ C1+ IN GND 8 V+ OUT 7 3.3µF 6 VIN 5 GND 3.3µF V- OUT Figure 4. Paralleling Two MAX864s Heavy Output Current Loads When under heavy loads, where V+ is sourcing current into V- (i.e., load current flows from V+ to V-, rather than from supply to ground), do not allow the V- supply to pull above ground.
PAGE 10
Dual-Output Charge Pump with Shutdown MAX864 ___________________Chip Topography C1- C2+ C1+ V+ GND 0.120" (3.05mm) C2VIN GND SHDN FC1 FC0 0.080" (2.
PAGE 11
Dual-Output Charge Pump with Shutdown DIM A A1 A2 B C D E e H h L N S α D A e A1 B S E INCHES MILLIMETERS MAX MIN MIN MAX 0.068 0.061 1.55 1.73 0.004 0.0098 0.127 0.25 0.061 0.055 1.40 1.55 0.012 0.008 0.20 0.31 0.0075 0.0098 0.19 0.25 SEE VARIATIONS 0.157 0.150 3.81 3.99 0.25 BSC 0.635 BSC 0.244 0.230 5.84 6.20 0.016 0.010 0.25 0.41 0.035 0.016 0.41 0.
PAGE 12
MAX864 Dual-Output Charge Pump with Shutdown Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are implied. Maxim reserves the right to change the circuitry and specifications without notice at any time. 12 __________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 (408) 737-7600 © 1996 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products.