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 PackageApplicationCellular Phones
GaAsFET Power Amplifier Modules
Personal Communicators, PDAs
Wireless Data Loggers
Continuously Adjustable GaAsFET Bias
LCD-Bias Contrast Control
Regulated Negative Power SuppliesPinout
SpecificationsSupply Voltage, VINto GND...........................................-0.3V to 10.5V
VNEGOUTto GND...........................................................-10.5V to 0.3V
VINto VNEGOUT................................................................0.3V to 21V
VOUTto GND (Note 1)................................................VNEGOUTto 0.3V
V SHDNto GND.....................................................-0.3V to (VIN+ 0.3V)
Continuous Power Dissipation (TA= +70°C)
SO (derate 5.88mW/°C above +70°C)....................................471mW
Operating Temperature Ranges
MAX84_I_ _A.............................................................-25°C to +85°C
MAX84_E_ _A............................................................-40°C to +85°C
Storage Temperature Range...................................-65°C to +150°C
Lead Temperature (soldering, 10sec)....................................+300°C
DescriptionThe max844 low-noise, inverting charge-pump power supplies are ideal for biasing GaAsFETs in cellular telephone transmitter amplifiers. max844 operate with inputs down to 2.5V. The MAX840 offers both a -2V preset output and a -0.5V to -9.4Vadjustable output.
The 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 max844 can operate with small capacitors, as low as 0.22µF.An internal linear regulator reduces the MAX840's out- put voltage ripple to 1mVp-p. With a well-filtered control voltage (VCTRL), the 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.
max844 Data Sheet
