SWITCHED CAPACITOR VOLTAGE CONVERTER January 30, 1998 TEL:805-498-2111 FAX:805-498-3804 WEB:http://www.semtech.com DESCRIPTION The SC1660 is a monolithic CMOS switched capacitor voltage converter. Designed to be an improved direct replacement for the popular 7660, the SC1660 provides performance superior to previous designs by combining low quiescent current with high efficiency, and by eliminating diode drop voltage losses. The only required external components are two low cost electrolytic capacitors. TEST CIRCUIT SC1660 FEATURES • Improved direct replacement for 7660 • Easy to use • 1.5V to 9V operation • No external diode required • Simple conversion of +5V to ±5V • Low quiescent current • High power efficiency • Boost pin for higher switching frequency APPLICATIONS • RS-232 power supplies • Handheld instruments • Data acquisition systems • Supply splitter, VOUT = ±VS/2 • Operational amplifier supplies ORDERING INFORMATION (1) DEVICE PACKAGE SC1660CN 8-Pin DIP SC1660CS SO-8 Note: (1) Add suffix ‘TR’ for tape and reel. PIN CONFIGURATION ABSOLUTE MAXIMUM RATINGS Parameter © 1997 SEMTECH CORP. Symbol Maximum Units Supply Voltage V+ 9.0 V Operating Temperature Range TA -40 to 85 °C Storage Temperature Range TSTG -65 to 125 °C 652 MITCHELL ROAD NEWBURY PARK CA 91320 SWITCHED CAPACITOR VOLTAGE CONVERTER SC1660 January 30, 1998 ELECTRICAL CHARACTERISTICS Unless otherwise specified, TA = 25°C, V+ = 5V, OSC = free running Parameter Symbol Conditions Min Input Voltage V+ RL=∞ 1.5 Supply Current IS RL=∞ Output Resistance ROUT Oscillator Frequency Pin 1=V+ Efficiency Voltage Conversion Efficiency Typ Max Units 9 V 35 70 µA IL=20mA, fOSC = 10kHz 45 90 Ω fOSC RL=∞ 10 50 kHz η RL = 5K, fOSC = 10kHz 96 98 % ηVOUT RL=∞ 98 99.9 % TYPICAL APPLICATIONS © 1997 SEMTECH CORP. • Negative Voltage Converter Figure 1 shows a typical connection which will provide a negative supply from an available positive supply without the need for any external diodes. The LV pin should be connected to ground for V+ ≤ 3V; for V+ > 3V it may be left floating. • Voltage Doubling Figure 2 shows a method of voltage doubling. Doubling is achieved by simply rearranging the connection of the two external capacitors. An external 500kΩ resistor is required to ensure the oscillator will start. • Ultra Precision Voltage Divider An ultra precision voltage divider is shown in Figure 3. To achieve the 0.0002% accuracy indicated, the load current should be kept below 100nA. However, with a slight loss in accuracy, the load current can be increased. • Battery Splitter A common need in many systems is to obtain positive and negative supplies from a single battery or power supply system. Where current requirements are small, the circuit shown in Figure 4 is a simple solution. 652 MITCHELL ROAD NEWBURY PARK CA 91320 SWITCHED CAPACITOR VOLTAGE CONVERTER SC1660 January 30, 1998 TYPICAL PERFORMANCE CHARACTERISTICS © 1997 SEMTECH CORP. 652 MITCHELL ROAD NEWBURY PARK CA 91320 SWITCHED CAPACITOR VOLTAGE CONVERTER SC1660 January 30, 1998 TYPICAL PERFORMANCE CHARACTERISTICS (cont.) OUTLINE DRAWING - 8-PIN DIP OUTLINE DRAWING - SO-8 © 1997 SEMTECH CORP. 652 MITCHELL ROAD NEWBURY PARK CA 91320