AIC1650 3-Cell, High-Efficiency, Inverting DC/DC Converter FEATURES 4V to 20V Input Voltage Operation. Adjustable Output Voltage up to -40V. Low Quiescent Current at 100µA. Pulse Frequency Modulation Maintains High Efficiency (max. 90%). 100KHz to 320KHz Switching Frequency. Power-Saving Shutdown Mode (8µA Typical). High Efficiency with Low Cost External PNP Bipolar Transistor. APPLICATIONS Negative LCD Contrast Bias for 1. Notebook & Palmtop Computers. 2. Pen-Based Data System. 3. Portable Data Collection Terminals. 4. Personal Digital Assistants. Negative Voltage Supply. DESCRIPTION The AIC1650 is a high performance inverting DC/DC converter, designed to drive an external power switch to generate programmable negative voltages. In the particularly suitable LCD bias contrast application, maximum efficiency of 90% can be achieved with low cost PNP bipolar transistor drivers. 4V to 20V input operation range allows the AIC1650 to be powered directly by the battery pack in most batteryoperated applications for greater efficiency. Output voltage can be scaled to -40V or greater by two external resistors. A pulse frequency modulation scheme is employed to maintain high efficiency conversion under wide input voltage range. Quiescent current is about 100µA and can be reduced to 8µA in shutdown mode. Switching frequency being around 100KHz to 320KHz range, small size switching components are ideal for battery powered portable equipments, like notebook and palmtop computers. TYPICAL APPLICATION CIRCUIT VIN +4V ~ 20V 100µF + C1 VIN CL VREF DHI SHDN DLOW FB 5V Q1 2N2907A D1 1N5819 RB 1.5K~12K GND *L 150µH AIC1650 0.047µF R2 100K C2 VOUT -12V~ -40V + R1 1M C4 100µF C3 * Sumida CD-54 SERIES VOUT = -1.22V x R1/R2 10nF Negative LCD Contrast Bias Power Supply Analog Integrations Corporation 4F, 9, Industry E. 9th Rd, Science Based Industrial Park, Hsinchu Taiwan, ROC DS-1650-02 Dec 27, 00 TEL: 886-3-5772500 FAX: 886-3-5772510 www.analog.com.tw 1 AIC1650 ORDERING INFORMATION AIC1650 XX PACKAGE TYPE N: PLASTIC DIP S: SMALL OUTLINE TEMPERATURE RANGE C=0°C~+70°C PIN CONFIGURATION ORDER NUMBER TOP VIEW AIC1650CN (PLASTIC DIP) AIC1650CS (PLASTIC SO) VIN 1 8 VREF 2 7 DHI SHDN 3 6 DLOW 4 5 GND FB CL ABSOLUTE MAXIMUM RATINGS Supply Voltage .................................................………….................................. 20V SHDN Voltage .............................................…………….................................... 15V Operating Temperature Range ..........................………........................... 0°C~ 70°C Storage Temperature Range ..................................………................ -65°C~ 150°C TEST CIRCUIT ELECTRICAL CHARACTERISTICS Refer to Typical Application Circuit. fied.) PARAMETER TEST CONDITIONS Input Voltage (VIN=13V, Ta=25°°C, unless otherwise speci- MIN. TYP. MAX. UNIT 20 V 100 200 µA 1.22 1.28 V 4 Switch Off Current VFB = -50mV VREF Voltage ISOURCE = 250µA VREF Source Current 1.16 µA 250 DLOW “ON Resistance” 15 Ω DHI “ON Resistance” 10 Ω CL Threshold 50 70 90 mV Shutdown Threshold 0.8 1.5 2.4 V 8 20 µA Shutdown Mode Current V SHDN =0V 2 AIC1650 TYPICAL PERFORMANCE CHARACTERISTICS 20 Shutdown Current (µA) Source Current (µA) Shutdown Current vs VIN VREF Source Current vs VIN 350 300 250 200 150 4 8 12 16 15 10 5 0 20 4 VIN (V) 8 10 12 14 16 18 20 Frequency vs VIN Voltage 330 280 Frequency (kHz) 90 Duty Cycle (%) 6 VIN (V) Duty Cycle vs VIN Voltage 100 (Ta=25°°C) 80 Ta=70°C 70 Ta=0°C Ta=0°C 230 Ta=25°C 180 Ta=70°C 130 60 Ta=25°C 50 80 4 8 12 16 20 4 8 12 VIN (V) 16 20 VIN (V) BLOCK DIAGRAM VIN VREF SHDN FB + 2 PFM OSCILLATOR 3 1.22V REFERENCE VOLTAGE 4 V IN CURRENT LIMIT COMPARATOR 1 LATCH V IN OUTPUT DRIVER + - 70mV 8 7 6 5 ERROR COMPARATOR CL DHI DLOW GND 3 AIC1650 PIN DESCRIPTIONS PIN 1: VIN PIN 6: DLOW - Driver sinking output. Connected to DHI when using an external P-channel MOSFET. When using an external PNP bipolar transistor, connect a resistor RB from this pin to DHI. RB value depends on VIN, inductor and PNP bipolar transistor. By adjusting the RB value, efficiency can be optimized. - 4V to 20V input supply voltage. PIN 2: VREF - 1.22V reference output. Bypass with a 0.047µF capacitor to GND. Sourcing capability is guaranteed to be greater than 250µA. PIN 3: SHDN- Logic input to shutdown the chip. >1.5V = normal operation, GND = shutdown In shutdown mode DLOW and DHI pins are at high level. PIN 4: FB - Feedback signal input to sense ground. Connecting a resistor R1 to VOUT and a resistor R2 to VREF pin yields the output voltage: PIN 7: DHI - Driver sourcing output. Connect to gate of the external P-channel MOSFET or base of the PNP bipolar transistor. PIN 8: CL - Current-limit input. This pin clamps the switch peak current to prevent over-current damage to the external switch. VOUT = -(R1/R2 ) x VREF PIN 5: GND - Power ground. APPLICATION INFORMATIONS Max. Output Power vs VIN The typical application circuit generates an adjustable 1.8 negative voltage for contrast bias of LCD displays. Typical Application Circuit 1.6 100µH 1.4 Max. Output Power (W) Efficiency and output power can be optimized by us- 120µH ing appropriate inductor and switch. The following 1.2 150µH 1 220µH 0.6 270µH 0.4 timal component values: L PNP : Inductor Value 4 6 8 10 12 VIN (V) 14 V IN I OUT × V OUT = (11.1 − 0.15 × V IN) × 300µH 330µH 0.2 0 formulas provide a guideline for determining the op- 180µH 0.8 16 18 20 V CEO > V IN + V OUT I C,MAX ≥ 200 × V CE < 0. 4V at I and β = 10 I OUT V IN C = 200 × IOUT V IN RB ≅ 3 x L x (VIN - 0.8) where, units: VIN & VOUT in V, IOUT in A, L in µH, RB in Ω 4 AIC1650 APPLICATION EXAMPLES Efficiency vs Load Current 95 Efficiency vs VIN 95 VOUT = -15V L =220µH VOUT =-15V IOUT =-10mA VIN=13V L=300µH 90 Efficiency (%) Efficiency (%) 90 VIN =8V 85 VIN=18V L=220µH L=150µH 85 80 75 0 5 10 15 20 25 80 30 4 8 6 90 20 L=220µH Efficiency (%) Efficiency (%) 18 VOUT =-22V IOUT =-10mA L=300µH VIN=13V VIN=8V 16 Efficiency vs VIN 95 VOUT =-22V L =220µH 90 14 VIN (V) Efficiency vs Load Current 95 12 10 Load Current (mA) VIN=18V 85 L=150µH 85 80 75 0 5 10 15 20 25 80 30 4 6 8 10 Efficiency vs Load Current 90 VIN=8V Efficiency (%) 80 5 10 15 18 20 L=220µH 90 85 0 16 20 Load Current (mA) VOUT = -30V IOUT = -10mA L=300µH VIN=13V VIN=18V 75 14 Efficiency vs VIN 95 95 VOUT = -30V L = 220µH 12 VIN (V) Load Current (mA) Efficiency (%) 25 30 L=150µH 85 80 4 6 8 10 12 14 16 18 20 VIN (V) 5 AIC1650 PHYSICAL DIMENSIONS 8 LEAD PLASTIC SO (unit: mm) D SYMBOL MIN MAX A 1.35 1.75 A1 0.10 0.25 B 0.33 0.51 C 0.19 0.25 D 4.80 5.00 E 3.80 4.00 H E e e A C A1 B 1.27(TYP) H 5.80 6.20 L 0.40 1.27 L 8 LEAD PLASTIC DIP (unit: mm) D E1 E A2 A1 C L eB b e SYMBOL MIN MAX A1 0.381 — A2 2.92 4.96 b 0.35 0.56 C 0.20 0.36 D 9.01 10.16 E 7.62 8.26 E1 6.09 7.12 e 2.54 (TYP) eB — 10.92 L 2.92 3.81 6