Description

The MAX840ESA is a low-noise, inverting charge-pump power supply that is specifically designed for biasing GaAsFETs in cellular telephone transmitter amplifiers. It provides a fixed output voltage of -2V or an adjustable output voltage range of -0.5V to -9.4V at 4mA. The input voltage range for this component is 2.5V to 10V, and it can operate with small capacitors as low as 0.22µF. The MAX840ESA ensures a low output voltage ripple of 1mVp-p and has a charge-pump switching frequency of 100kHz in normal operation and 20kHz in shutdown mode (MAX844). It also features a logic-level shutdown over temperature with a maximum current of 1µA. This component is available in a small 8-pin SO package.

Specifications and features

• Output Voltage: Fixed -2V or Adjustable -0.5V to -9.4V
• Output Current: 4mA
• Input Voltage Range: 2.5V to 10V
• Capacitor Compatibility: as low as 0.22µF
• Output Voltage Ripple: 1mVp-p
• Charge-Pump Switching Frequency:
  • Normal Operation: 100kHz
  • Shutdown Mode (MAX844): 20kHz
• Logic-Level Shutdown Current (MAX840/MAX843): 1µA (max) over temperature
• Package: Small 8-Pin SO

Application Scenarios

The MAX840ESA is commonly used in the following applications:

• Cellular Phones
• GaAsFET Power Amplifier Modules
• Personal Communicators, PDAs
• Wireless Data Loggers
• Continuously Adjustable GaAsFET Bias
• LCD-Bias Contrast Control
• Regulated Negative Power Supplies

Comparison

The advantages and disadvantages of the MAX840ESA are:

• Low-noise power supply specifically designed for biasing GaAsFETs
• Wide input voltage range and small capacitor compatibility
• Low output voltage ripple
• Logic-level shutdown with low current consumption over temperature
• Compact and convenient 8-pin SO package

• Fixed output voltage may not be suitable for all applications