MAX844

Low-Noise, Regulated, -2V GaAsFET Bias

Operates with Small Capacitors, as Low as 0.22 µF


Please check latest availability status for a specific part variant.

Description

The MAX840/MAX843/MAX844 low-noise, inverting charge-pump power supplies are ideal for biasing GaAsFETs in cellular telephone transmitter amplifiers. They operate with inputs down to 2.5V.

The MAX840 offers both a -2V preset output and a -0.5V to -9.4V adjustable output. The MAX843/MAX844 use an external positive control voltage to set the negative output voltage. Input voltage range for all the devices is 2.5V to 10V, and output current is 4mA with VIN > 2.7V. These circuits can operate with small capacitors, as low as 0.22µF.

An internal linear regulator reduces the MAX840's output voltage ripple to 1mVp-p. With a well-filtered control voltage (VCTRL), the MAX843/MAX844 also achieve less than 1mVp-p typical output ripple. Supply current is 750µA, and reduces to less than 1µA in shutdown (MAX840/MAX843). The MAX844's unregulated output is active in shutdown, with the charge pump switching at 20kHz. It provides a low-power LCD supply.
MAX840, MAX843, MAX844: Typical Operating Circuit MAX840, MAX843, MAX844: Typical Operating Circuit Enlarge+

Key Features

  • Fixed -2V or Adjustable -0.5V to -9.4V Output at 4mA (MAX840)
  • 2.5V to 10V Input Voltage Range
  • Operate with Small Capacitors (as low as 0.22µF)
  • 1mVp-p Output Voltage Ripple
  • Charge-Pump Switching Frequency:
    • 100kHz in Normal Operation
    • 20kHz in Shutdown Mode (MAX844)
  • 1µA Max Logic-Level Shutdown Over Temp. (MAX840/MAX843)
  • Small 8-Pin SO Package

Applications/Uses

  • Cell Phones
  • Continuously Adjustable GaAsFET Bias
  • GaAsFET Power Amplifier Modules
  • LCD-Bias Contrast Control
  • Personal Communicators, PDAs
  • Regulated Negative Power Supplies
  • Wireless Data Loggers
Part NumberTopologyVIN
(V)
VIN
(V)
ICC
(mA)
Unadj. VOUT
(V)
Adj. VOUT
(V)
Adj. VOUT
(V)
IOUT
(A)
Oper. Freq.
(kHz)
Oper. Temp.
(°C)
Package/PinsBudgetary
Price
minmaxmaxminmaxtypSee Notes
MAX840 
Inverter
Regulated
2.5101.3-2-VIN-0.6-0.50.01100
-40 to +85
-20 to +85
SOIC(N)/8
$1.75 @1k
MAX843 
Inverter
Regulated
SOIC(N)/8
$1.75 @1k
MAX844 Regulated
SOIC(N)/8
-
See All Charge Pumps (44)
Pricing Notes:
This pricing is BUDGETARY, for comparing similar parts. Prices are in U.S. dollars and subject to change. Quantity pricing may vary substantially and international prices may differ due to local duties, taxes, fees, and exchange rates. For volume-specific and version-specific prices and delivery, please see the price and availability page or contact an authorized distributor.


MAX840EVKIT: Evaluation Kit for the MAX840, MAX843, MAX844
MAX843EVKIT: Evaluation Kit for the MAX840, MAX843, MAX844
MAX844EVKIT: Evaluation Kit for the MAX840, MAX843, MAX844

Technical Documents

Tutorial 4803 The Basics of USB Battery Charging: A Survival Guide

Quality and Environmental Data

Request Reliability Report for: MAX844 
Lead-Free Package Tin (Sn) Whisker Reports
Device   Fab Process   Technology   Sample size   Rejects   FIT at 25°C   FIT at 55°C  

Note : The failure rates are summarized by technology and mapped to the associated material part numbers. The failure rates are highly dependent on the number of units tested.

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