a FEATURES Inverts Input Supply Voltage 99% Voltage Conversion Efficiency 25 mA Output Current Shutdown Function Requires Only Two Capacitors 1 mF Capacitors 18 V Output Resistance +1.5 V to +5.5 V Input Range 600 mA Quiescent Current 20 nA Shutdown Current (ADM8828) Switched-Capacitor Voltage Inverter with Shutdown ADM8828/ADM8829 FUNCTIONAL BLOCK DIAGRAMS OUT 1 IN 2 6 CAP+ ADM8828 5 SHDN TOP VIEW (Not to Scale) 4 CAP– 3 GND OUT 1 IN 2 6 CAP+ ADM8829 5 NC TOP VIEW (Not to Scale) 4 CAP– 3 GND APPLICATIONS Handheld Instruments LCD Panels Cellular Phones PDAs Remote Data Acquisition Op Amp Power Supplies NC = NO CONNECT GENERAL DESCRIPTION The ADM8828/ADM8829 is a charge-pump voltage inverter which may be used to generate a negative supply from a positive input. Input voltages ranging from +1.5 V to +5.5 V can be inverted into a negative –1.5 V to –5.5 V output supply. This inverting scheme is ideal for generating a negative rail in single power-supply systems. Only two small external capacitors are needed for the charge pump. Output currents up to 25 mA with greater than 99% efficiency are achievable. The ADM8828 also features a low power shutdown (SHDN) pin. This can be used to disable the device and reduce the quiescent current to 20 nA. +1.5V TO +5.5V INPUT CAP+ C1 + 1mF IN ADM8828/ ADM8829 CAP– GND SHDN SHUTDOWN CONTROL OUT C2 + 1mF INVERTED NEGATIVE OUTPUT Figure 1. Typical Circuit Configuration The ADM8828/ADM8829 is available in a 6-lead SOT-23 package. REV. A Information furnished by Analog Devices is believed to be accurate and reliable. However, no responsibility is assumed by Analog Devices for its use, nor for any infringements of patents or other rights of third parties which may result from its use. No license is granted by implication or otherwise under any patent or patent rights of Analog Devices. One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A. Tel: 781/329-4700 World Wide Web Site: http://www.analog.com Fax: 781/326-8703 © Analog Devices, Inc., 1999 ADM8828/ADM8829–SPECIFICATIONS Parameter Min Input Voltage, IN 1.5 Supply Current Output Current Output Resistance Output Ripple 25 Charge-Pump Frequency 50 65 Power Efficiency Voltage Conversion Efficiency 99.5 Shutdown Supply Current, ISHDN Shutdown Input Voltage, VSHDN 2.0 Typ (VIN = +5 V, C1, C2 = 1 mF,1 TA = TMIN to TMAX unless otherwise noted) Max Units Test Conditions/Comments 5.5 V RL = 10 kΩ 600 1000 µA Unloaded 18 25 130 28 mA Ω mV p-p mV p-p IL = 5 mA IL = 5 mA IL = 25 mA 120 190 kHz kHz VIN = +2.25 V % % % % % RL = 200 Ω RL = 1 kΩ No Load RL = 1 kΩ RL = 200 Ω µA V V µs SHDN = IN SHDN High = Disabled SHDN Low = Enabled IL = 5 mA 90 87 99.96 98 91 0.02 2 0.8 Shutdown Exit Time 175 NOTES 1 C1 and C2 are low ESR (<0.2 Ω) electrolytic capacitors. High ESR will degrade performance. Specifications subject to change without notice. PIN FUNCTION DESCRIPTIONS ABSOLUTE MAXIMUM RATINGS* (TA = +25°C unless otherwise noted) Input Voltage (IN to GND) . . . . . . . . . . . . . . . –0.3 V to +6 V OUT to GND . . . . . . . . . . . . . . . . . . . . . . . . –6.0 V to +0.3 V OUT, IN Output Current (Continuous) . . . . . . . . . . . . 50 mA Output Short Circuit Duration to GND . . . . . . . . . . . 10 secs Power Dissipation, RT-6 . . . . . . . . . . . . . . . . . . . . . . 570 mW (Derate 8.3 mW/°C above +70°C) θJA, Thermal Impedance . . . . . . . . . . . . . . . . . . . . 120°C/W Operating Temperature Range Industrial (A Version) . . . . . . . . . . . . . . . . – 40°C to +85°C Storage Temperature Range . . . . . . . . . . . –65°C to +150°C Lead Temperature Range (Soldering 10 sec) . . . . . . . . +300°C Vapor Phase (70 sec) . . . . . . . . . . . . . . . . . . . . . . . . +215°C Infrared (15 sec) . . . . . . . . . . . . . . . . . . . . . . . . . . . . +220°C ESD Rating . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . >3500 V *This is a stress rating only and functional operation of the device at these or any other conditions above those indicated in the operation section of this specification is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability. Mnemonic Function CAP+ GND CAP– OUT SHDN Positive Charge-Pump Capacitor Terminal. Power Supply Ground. Negative Charge-Pump Capacitor Terminal. Output, Negative Voltage. Shutdown Control Input. This input, when high, is used to disable the charge pump thereby reducing the power consumption. Positive Power Supply Input. IN PIN CONFIGURATIONS OUT 1 6 CAP+ ADM8828 5 SHDN IN 2 TOP VIEW (Not to Scale) 4 CAP– 3 GND ORDERING GUIDE Model Temperature Range Branding Information Package Option* ADM8828ART ADM8829ART –40°C to +85°C –40°C to +85°C MM0 MN0 RT-6 RT-6 OUT 1 IN 2 6 CAP+ ADM8829 5 NC TOP VIEW (Not to Scale) 4 CAP– 3 GND NC = NO CONNECT *RT-6 = 6-lead SOT-23. –2– REV. A Typical Performance Characteristics– ADM8828/ADM8829 60 0.8 IL = 5mA OUTPUT VOLTAGE RIPPLE – mV p-p SUPPLY CURRENT – mA 0.7 0.6 0.5 0.4 0.3 0.2 50 OUTPUT VOLTAGE RIPPLE @ VIN = 4.75V 40 OUTPUT VOLTAGE RIPPLE @ VIN = 1.9V 30 20 OUTPUT VOLTAGE RIPPLE @ VIN = 3.15V 10 0.1 0 1 1.5 2 2.5 3 3.5 4 SUPPLY VOLTAGE – V 4.5 5 0 0.47 5.5 Figure 2. Power Supply Current vs. Voltage 350 OUTPUT VOLTAGE RIPPLE – mV p-p OUTPUT RESISTANCE – V 30 25 20 15 10 5 2 2.5 3 3.5 4 SUPPLY VOLTAGE – V 4.5 5 5.5 150 100 50 3.3 OUTPUT VOLTAGE @ VIN = 2.0V –1 OUTPUT VOLTAGE – V OUTPUT CURRENT – mA OUTPUT VOLTAGE RIPPLE @ VIN = 3.15V, VOUT = –2.5V 200 –0.5 OUTPUT CURRENT @ VIN = 4.75V 14 OUTPUT CURRENT @ VIN = 3.15V 10 8 OUTPUT CURRENT @ VIN = 1.9V –1.5 –2 OUTPUT VOLTAGE @ VIN = 3.3V –2.5 –3 –3.5 4 –4 2 –4.5 0 0.47 2.2 1 CAPACITANCE – mF –5 3.3 Figure 4. Output Current vs. Capacitance REV. A 250 0 16 6 OUTPUT VOLTAGE RIPPLE @ VIN = 4.75V, VOUT = –4.0V Figure 6. Output Voltage Ripple vs. Capacitance 20 12 300 OUTPUT VOLTAGE RIPPLE @ VIN = 1.9V, VOUT = –1.5V 0 2.2 0.47 1 CAPACITANCE – mF Figure 3. Output Source Resistance vs. Supply Voltage 18 3.3 Figure 5. Output Voltage Ripple vs. Capacitance 35 0 1.5 1 2.2 CAPACITANCE – mF OUTPUT VOLTAGE @ VIN = 5.0V 0 5 10 15 20 25 30 OUTPUT CURRENT – mA 35 40 Figure 7. Output Voltage vs. Output Current –3– 45 ADM8828/ADM8829 100 200 PEFF @ VIN = 5.0V 180 80 160 PEFF – % 70 PUMP FREQUENCY – kHz 90 PEFF @ VIN = 3.3V 60 PEFF @ VIN = 2.0V 50 40 30 100 60 10 20 5 10 15 20 25 30 IOUT – mA 35 40 45 0 –50 50 Figure 8. Power Efficiency vs. Output Current PUMP FREQUENCY @ VIN = 1.5V 80 40 0 PUMP FREQUENCY @ VIN = 5.0V 120 20 0 PUMP FREQUENCY @ VIN = 3.3V 140 –30 –10 10 25 40 60 80 TEMPERATURE – 8C 90 110 125 Figure 10. Charge Pump Frequency vs. Temperature 50 45 RESISTANCE (V) @ VIN = 1.5V OUTPUT RESISTANCE – V 40 35 30 RESISTANCE (V) @ VIN = 3.3V 25 20 RESISTANCE (V) @ VIN = 5.0V 15 10 5 0 –50 –30 –10 10 25 40 60 80 TEMPERATURE – 8C 90 110 125 Figure 9. Output Resistance vs. Temperature –4– REV. A ADM8828/ADM8829 GENERAL INFORMATION Capacitor Selection The ADM8828/ADM8829 is a switched capacitor voltage converter that can be used to invert the input supply voltage. The flying capacitor C1 can be increased to reduce the output resistance. The voltage conversion task is achieved using a switched capacitor technique using two external charge storage capacitors. An on-chip oscillator and switching network transfers charge between the charge storage capacitors. The basic principle behind the voltage conversion scheme is illustrated below. The output capacitor size C2 affects the output ripple. Increasing the capacitor size reduces the peak-peak ripple. The ESR affects both the output impedance and the output ripple. V+ CAP+ S1 Reducing the ESR reduces the output impedance and ripple. For convenience it is recommended that both C1 and C2 be the same value. S3 The ac impedance of the ADM8828/ADM8829 may be reduced by using a bypass capacitor on the input supply. This capacitor should be connected between the input supply and GND. It will provide instantaneous current surges as required. Suitable capacitors of 1 µF or greater may be used. + C1 S2 S4 + CAP– F1 42 OSCILLATOR OUT = –V+ C2 F2 Figure 11. Voltage Inversion Principle +1.5V TO +5.5V INPUT An oscillator generating antiphase signals φ1 and φ2 controls switches S1, S2 and S3, S4. During φ1, switches S1 and S2 are closed while S3 and S4 are open, thereby charging C1 up to the voltage at V+. During φ2, S1 and S2 open and S3 and S4 close. The positive terminal of C1 is connected to GND via S3 during this phase and the negative terminal of C1 connects to VOUT via S4. The net result is voltage inversion at VOUT wrt GND. Charge on C1 is transferred to C2 during φ2. Capacitor C2 maintains this voltage during φ1. The charge transfer efficiency depends on the on-resistance of the switches, the frequency at which they are being switched and also on the equivalent series resistance (ESR) of the external capacitors. For maximum efficiency, capacitors with low ESR are, therefore, recommended. CAP+ C1 + 1mF CAP– GND SHDN SHUTDOWN CONTROL OUT C2 + 1mF INVERTED NEGATIVE OUTPUT Figure 12. Typical Circuit Configuration Shutdown Input The ADM8828 contains a shutdown input that can be used to disable the device and hence reduce the power consumption. A logic high level on the SHDN input shuts the device down reducing the quiescent current to 0.02 µA. During shutdown the output voltage discharges to 0 V. Therefore, ground referenced loads are not powered during this state. When exiting shutdown, it takes several cycles (approximately 175 µs) for the charge pump to reach its final value. If the shutdown function is not being used, SHDN should be hardwired to GND. REV. A IN ADM8828/ ADM8829 –5– ADM8828/ADM8829 OUTLINE DIMENSIONS Dimensions shown in inches and (mm). 6-Lead SOT-23 (RT-6) 0.071 (1.80) 0.059 (1.50) 6 5 4 1 2 3 C3352a–0–10/99 0.122 (3.10) 0.106 (2.70) 0.118 (3.00) 0.098 (2.50) PIN 1 0.037 (0.95) BSC 0.075 (1.90) BSC 0.006 (0.15) 0.000 (0.00) 0.057 (1.45) 0.035 (0.90) 0.020 (0.50) SEATING 0.010 (0.25) PLANE 108 0.009 (0.23) 08 0.003 (0.08) 0.022 (0.55) 0.014 (0.35) PRINTED IN U.S.A. 0.051 (1.30) 0.035 (0.90) –6– REV. A