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General Description

The ultra-small MAX828/MAX829 monolithic, CMOS

charge-pump inverters accept input voltages ranging

from +1.5V to +5.5V. The MAX828 operates at 12kHz,

and the MAX829 operates at 35kHz. Their high efficiency

(greater than 90% over most of the load-current range)

and low operating current (60µA for the MAX828) make

these devices ideal for both battery-powered and board-

level voltage-conversion applications.

The MAX828/MAX829 combine low quiescent current

and high efficiency. Oscillator control circuitry and four

power MOSFET switches are included on-chip.

Applications include generating a -5V supply from a +5V

logic supply to power analog circuitry. Both parts come

in a 5-pin SOT23-5 package and can deliver 25mA with

a voltage drop of 500mV.

For a similar device with logic-controlled shutdown,

refer to the MAX1719/MAX1720/MAX1721. For applica-

tions requiring more power, the MAX860 delivers up to

50mA with a voltage drop of 600mV, in a space-saving

µMAX package.

Applications

Small LCD Panels

Cell Phones

Medical Instruments

Handy-Terminals, PDAs

Battery-Operated Equipment

Features

♦ 5-Pin SOT23-5 Package

♦ 95% Voltage Conversion Efficiency

♦ Inverts Input Supply Voltage

♦ 60µA Quiescent Current (MAX828)

♦ +1.5V to +5.5V Input Voltage Range

♦ Requires Only Two Capacitors

♦ 25mA Output Current

MAX828/MAX829

Switched-Capacitor Voltage Inverters

________________________________________________________________ Maxim Integrated Products 1

TOP VIEW

GND

C1-

C1+

OUT

SOT23-5

MAX828

MAX829

Pin Configuration

NEGATIVE VOLTAGE CONVERTER

C1+

C1-

OUT

GND

INPUT

SUPPLY

VOLTAGE

NEGATIVE

OUTPUT

VOLTAGE

MAX828

MAX829

Typical Operating Circuit

19-0495; Rev 3; 9/99

PART

MAX828EUK

-40°C to +85°C

TEMP. RANGE

PIN-

PACKAGE

5 SOT23-5

Ordering Information

MAX829EUK

-40°C to +85°C 5 SOT23-5

SOT

TOP MARK

AABI

AABJ

For price, delivery, and to place orders, please contact Maxim Distribution at 1-888-629-4642,

or visit Maxim’s website at www.maxim-ic.com.

Summary of content (8 pages)

PAGE 1
9-0495; Rev 3; 9/99 Switched-Capacitor Voltage Inverters Applications Features ♦ 5-Pin SOT23-5 Package ♦ 95% Voltage Conversion Efficiency ♦ Inverts Input Supply Voltage ♦ 60µA Quiescent Current (MAX828) ♦ +1.5V to +5.5V Input Voltage Range ♦ Requires Only Two Capacitors ♦ 25mA Output Current Ordering Information PART TEMP.
PAGE 2
MAX828/MAX829 Switched-Capacitor Voltage Inverters ABSOLUTE MAXIMUM RATINGS IN to GND .................................................................+6.0V, -0.3V OUT to GND .............................................................-6.0V, +0.3V OUT Output Current ...........................................................50mA OUT Short-Circuit to GND ............................................Indefinite Continuous Power Dissipation (TA = +70°C) SOT23-5 (derate 7.1mW/°C above +70°C)...................
PAGE 3
Switched-Capacitor Voltage Inverters 20 MAX828 15 10 25 0 4.5 VIN = 3.3V 20 10 3.5 MAX828/829-02 30 15 2.5 VIN = 1.5V 35 5 1.5 VIN = 5.0V VIN = 3.15V, VOUT = -2.5V 30 25 20 15 VIN = 1.9V, VOUT = -1.5V 10 5 0 -40 5.5 35 -20 0 20 40 60 80 0 5 10 15 20 25 30 35 40 45 50 SUPPLY VOLTAGE (V) TEMPERATURE (°C) CAPACITANCE (µF) MAX829 OUTPUT CURRENT vs. CAPACITANCE MAX828 OUTPUT VOLTAGE RIPPLE vs. CAPACITANCE MAX829 OUTPUT VOLTAGE RIPPLE vs. CAPACITANCE 35 VIN = 3.15V, V- = -2.
PAGE 4
Typical Operating Characteristics (continued) (Circuit of Figure 1, VIN = +5V, C1 = C2 = C3, TA = +25°C, unless otherwise noted.) OUTPUT VOLTAGE vs. OUTPUT CURRENT -0.5 VIN = 3.3V -2.5 -3.5 80 EFFICIENCY (%) VIN = 2.0V -1.5 VIN = 5.0V 90 VIN = 3.3V VIN = 2.0V 70 MAX828/829-11 EFFICIENCY vs. OUTPUT CURRENT 100 MAX828/829-10 0.5 OUTPUT VOLTAGE (V) 60 50 40 30 VIN = 5.0V 20 -4.5 10 0 -5.
PAGE 5
Switched-Capacitor Voltage Inverters S1 Charge-Pump Output VOUT = -(VIN - VDROOP-) Efficiency Considerations The efficiency of the MAX828/MAX829 is dominated by its quiescent supply current (IQ) at low output current and by its output impedance (ROUT) at higher output current; it is given by: η≅ IOUT  IOUT x ROUT  1−  IOUT + IQ  VIN  S2 IN During the first half-cycle, switches S2 and S4 open, switches S1 and S3 close, and capacitor C1 charges to the voltage at IN (Figure 2).
PAGE 6
MAX828/MAX829 Switched-Capacitor Voltage Inverters Flying Capacitor (C1) Increasing the flying capacitor’s size reduces the output resistance. Small C1 values increase the output resistance. Above a certain point, increasing C1’s capacitance has a negligible effect, because the output resistance becomes dominated by the internal switch resistance and capacitor ESR. Output Capacitor (C2) Increasing the output capacitor’s size reduces the output ripple voltage.
PAGE 7
Switched-Capacitor Voltage Inverters … C1 … +VIN 2 2 3 3 4 4 MAX828 MAX829 “1” 5 C1 1 MAX828/MAX829 ROUT OF SINGLE DEVICE ROUT = NUMBER OF DEVICES +VIN 2 MAX828 MAX829 “n” 5 2 3 3 1 … VOUT C2 C1 4 5 MAX828 MAX829 “1” 4 C1 1 5 MAX828 MAX829 “n” 1 VOUT C2 … VOUT = -nVIN VOUT = -VIN Figure 4. Cascading MAX828s or MAX829s to Increase Output Voltage C2 Figure 5.
PAGE 8
Chip Information INPUT 3 C1 5 4 C1- IN 2 CIN 0.1µF MAX828 C1+ MAX829 GND SHUTDOWN LOGIC SIGNAL TRANSISTOR COUNT: 58 SUBSTRATE CONNECTED TO IN OFF ON OUT 1 OUTPUT C2 Figure 8. Shutdown Control Package Information SOT5L.EPS MAX828/MAX829 Switched-Capacitor Voltage Inverters Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are implied.