MAX840/MAX843/MAX844 19-0388 Rev 1 3/96 Low-Noise, Regulated, -2V GaAsFET Bias General Description Features The MAX840/MAX843/MAX844 low-noise, inverting Fixed -2V or Adjustable -0.5V to -9.4V Output charge-pump power supplies are ideal for biasing at 4mA (MAX840) GaAsFETs in cellular telephone transmitter amplifiers. They operate with inputs down to 2.5V. 2.5V to 10V Input Voltage Range The MAX840 offers both a -2V preset output and a -0.5V Operate with Small Capacitors (as low as 0.22F) to -9.4V adjustable output. The MAX843/MAX844 use 1mVp-p Output Voltage Ripple an external positive control voltage to set the negative output voltage. Input voltage range for all the devices is Charge-Pump Switching Frequency: 2.5V to 10V, and output current is 4mA with V > 2.7V. IN 100kHz in Normal Operation These circuits can operate with small capacitors, as low 20kHz in Shutdown Mode (MAX844) as 0.22F. An internal linear regulator reduces the MAX840s out- 1A Max Logic-Level Shutdown Over Temp. put voltage ripple to 1mVp-p. With a well-filtered control (MAX840/MAX843) voltage (V ), the MAX843/MAX844 also achieve less CTRL Small 8-Pin SO Package than 1mVp-p typical output ripple. Supply current is 750A, and reduces to less than 1A in shutdown (MAX840/MAX843). The MAX844s unregulated output is active in shutdown, with the charge pump switching at Ordering Information 20kHz. It provides a low-power LCD supply. PART TEMP. RANGE PIN-PACKAGE Applications MAX840C/D 0C to +70C Dice* Cellular Phones MAX840ISA -25C to +85C 8 SO GaAsFET Power Amplifier Modules MAX840ESA -40C to +85C 8 SO Personal Communicators, PDAs MAX843C/D 0C to +70C Dice* Wireless Data Loggers MAX843ISA -25C to +85C 8 SO Continuously Adjustable GaAsFET Bias MAX843ESA -40C to +85C 8 SO LCD-Bias Contrast Control MAX844C/D 0C to +70C Dice* Regulated Negative Power Supplies MAX844ISA -25C to +85C 8 SO MAX844ESA -40C to +85C 8 SO Typical Operating Circuit * Dice are specified at T = +25C only. A V = 2.5V to 10.0V IN (3 CELLS) Pin Configuration 0.22F IN C1+ TOP VIEW V = -2.0V OUT 0.22F (V of GaAsFET) GG MAX840 OUT C1- 1 8 C1+ IN 4.7F NEGOUT C1- 2 7 GND MAX840 0.22F MAX843 NEGOUT 3 6 OUT MAX844 SHDN 4 5 FB (CONT) ON/OFF SHDN FB SO GND ( ) ARE FOR MAX843/MAX844 Maxim Integrated Products 1 For free samples & the latest literature: Low-Noise, Regulated, -2V GaAsFET Bias ABSOLUTE MAXIMUM RATINGS Supply Voltage, V to GND ..................................-0.3V to 10.5V Operating Temperature Ranges IN V to GND...................................................-10.5V to 0.3V MAX84 I A ...................................................-25C to +85C NEGOUT V to V .........................................................-0.3V to 21V MAX84 E A ..................................................-40C to +85C IN NEGOUT V to GND (Note 1).......................................V to 0.3V Storage Temperature Range .............................-65C to +150C OUT NEGOUT V to GND ............................................-0.3V to (V + 0.3V) Lead Temperature (soldering, 10sec) .............................+300C SHDN IN Continuous Power Dissipation (T = +70C) A SO (derate 5.88mW/C above +70C).........................471mW Note 1: The output may be shorted to NEGOUT or GND if the package power dissipation is not exceeded. Typical short-circuit current from 4V to GND is 40mA. Stresses beyond those listed under Absolute Maximum Ratings may cause permanent damage to the device. These are stress ratings only, and functional operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability. ELECTRICAL CHARACTERISTICS (Figures 2a and 2c, 2.5V V 10V, V = -2V, GND = 0V, R = , SHDN = V , T = T to T , unless otherwise noted. IN OUT L IN A MIN MAX Typical values are measured at V = 3.6V and T = +25C.) IN A PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS Supply Voltage Range V 2.5 10 V IN V 2.5V, IN -2.1 -2.0 -1.9 I = 0mA to 3mA OUT MAX840, V = 0V FB V 2.7V, IN -2.1 -2.0 -1.9 I = 0mA to 4mA OUT Output Voltage V V OUT V 2.5V, IN -2.05 -2.0 -1.95 I = 0mA to 3mA OUT MAX843/MAX844, V = 2V CTRL V 2.7V, IN -2.05 -2.0 -1.95 I = 0mA to 4mA OUT -0.5 to Output Voltage Adjust Range V V OUT (V - 0.6) IN FB Voltage V MAX840, no load -0.516 -0.5 -0.484 V FB FB Leakage Current I MAX840, V = -0.5V 1 100 nA FB FB CONT Leakage Current I MAX843/MAX844, V = 0V 1 100 nA CONT CONT Supply Current I No load, V 3.6V 750 1300 A Q IN MAX840/MAX843, V = 10V, SHDN = 0V 1 IN Shutdown Supply Current I MAX844, V = 10V, SHDN = 0V 940 A SHUT IN MAX844, V 3.6V, SHDN = 0V 175 300 IN MAX840, V = 0V 38 FB V = 3.6V, IN V Load Regulation mV/mA OUT MAX843/MAX844, R = or 500 L 28 V = 2V CTRL V Ripple C4 = 10F 1 mVp-p OUT MAX840/MAX843/ 80 100 120 V = 3.6V, IN MAX844 Oscillator Frequency F kHz OSC T = +25C A MAX844, SHDN = 0V 14 20 26 Input High Voltage V SHDN 2.2 V IH Input Low Voltage V SHDN 0.35 V IL Input Current I SHDN -1 1 A IN Input Capacitance C SHDN 10 pF IN 2 MAX840/MAX843/MAX844