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MAX840, MAX843, MAX844
Low-Noise, Regulated, -2V GaAsFET Bias
Operates with Small Capacitors, as Low as 0.22 µF
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Status
Active: In Production.
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.
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Data Sheet
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An evaluation kit is available: MAX840EVKIT, MAX843EVKIT, MAX844EVKIT
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
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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
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Key Specifications:
| Charge Pumps |
| Part Number |
Topology |
VIN
(V) |
VIN
(V) |
ICC
(mA) |
Unadj. VOUT
(V) |
Adj. VOUT
(V) |
Adj. VOUT
(V) |
IOUT
(A) |
Oper. Freq.
(kHz) |
Oper. Temp.
(°C) |
Package/Pins |
Smallest Available Pckg.
(mm2) |
Budgetary Price |
| min |
max |
max |
min |
max |
typ |
max w/pins |
See Notes |
| MAX840 |
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2.5 |
10 |
1.3 |
-2 |
-VIN-0.6 |
-0.5 |
0.01 |
100 |
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30.9 |
$1.75 @1k |
| MAX843 |
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$1.75 @1k |
| MAX844 |
Regulated |
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$2.37 @1k |
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See All Charge Pumps (45)
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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 prices and delivery, please see the price and availability page or contact an authorized distributor.
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Diagram
 Typical Operating Circuit
Didn't Find What You Need?
Information Index
Document Ref.: 19-0388
Rev 1;
1996-03-01
This page last modified: 2007-07-17
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