LOW VOLTAGE STEP-UP DC-DC CONVERTER January 29, 1998 SC1631 TEL:805-498-2111 FAX:805-498-3804 WEB:http://www.semtech.com DESCRIPTION The SC1631 is a high efficiency step up DC-DC converter. Only four external components are required to deliver a fixed voltage of 3V, 3.3V, or 5V. Efficiency beyond 87% can be easily achieved at 100mA load with 2.2V to 3V input voltages. A logic-controlled shutdown mode is provided for power saving. Switch current limit can be programmed with a resistor. The low battery detector can be configured as a linear regulator or a burst mode controller providing extremely low supply current operation. FEATURES • High efficiency 90% • Power-saving shutdown mode (7µA typical) • Internal 2A switch • 120kHz switching rate • Adjustable switch current limit • On-chip low battery detector A switching rate of 120kHz reduces the inductor size inductors of 25µH to 50µH are recommended for most applications. APPLICATIONS • Palmtop and notebook computers • Pocket organizers • Cameras • Pagers • Battery backup supplies • Portable instruments BLOCK DIAGRAM ORDERING INFORMATION (1) DEVICE OUTPUT VOLTAGE PACKAGE 3.3V 3.0V 5.0V SO-8 SC1631CS SC1631-3CS SC1631-5CS Note: (1) Add suffix ‘TR’ for tape and reel. PIN CONFIGURATION ABSOLUTE MAXIMUM RATINGS Parameter © 1997 SEMTECH CORP. Symbol Maximum Units Supply Voltage VIN 7.0 V Operating Temperature Range TA 0 to 70 °C Storage Temperature Range TSTG -65 to 125 °C 652 MITCHELL ROAD NEWBURY PARK CA 91320 LOW VOLTAGE STEP-UP DC-DC CONVERTER SC1631 January 29, 1998 ELECTRICAL CHARACTERISTICS Unless otherwise specified, TA = 25°C, VIN = 3.0V Test Conditions Parameter VIN Test Limits IL Max Units 7.0 V 3.30 3.00 5.00 3.44 3.12 5.20 V Switch Off Current 105 140 µA No Load Current SC1631/SC1631-3 SC1631-5 160 180 Input Voltage Min 1.5 Output Voltage SC1631 SC1631-3 SC1631-5 IL = 200mA 3.16 2.88 4.80 Shutdown Mode Current Recovery Time from Shutdown 7 VIN=2.5V Efficiency SC1631/SC1631-3 SC1631-5 Line Regulation SC1631 SC1631-3 SC1631-5 VIN=1.8 - 3.3V VIN=1.8 - 3.0V VIN=2.2 - 3.3V Load Regulation SC1631/SC1631-3 SC1631-5 Oscillator Frequency LBI Pin Trip Point LBO “On Resistance” SW “On Resistance” SC1631/SC1631-3 SC1631-5 Typ VIN = 2V µA 15 µA IL=200mA 0.4 ms IL=200mA 87 90 % IL=100mA 0.6 0.5 0.8 %VOUT IL=10mA - 300mA 0.3 0.8 %VOUT 90 120 150 kHz 1.17 1.22 1.27 V 45 Ω 0.5 0.4 Ω SW Off Leakage 1 µA Input Pin Bias Current 10 nA/Pin Output Pin Leakage 10 nA/Pin © 1997 SEMTECH CORP. 652 MITCHELL ROAD NEWBURY PARK CA 91320 LOW VOLTAGE STEP-UP DC-DC CONVERTER SC1631 January 29, 1998 TYPICAL PERFORMANCE CHARACTERISTICS © 1997 SEMTECH CORP. 652 MITCHELL ROAD NEWBURY PARK CA 91320 LOW VOLTAGE STEP-UP DC-DC CONVERTER SC1631 January 29, 1998 TYPICAL PERFORMANCE CHARACTERISTICS (cont.) TYPICAL APPLICATION CIRCUIT © 1997 SEMTECH CORP. 652 MITCHELL ROAD NEWBURY PARK CA 91320 LOW VOLTAGE STEP-UP DC-DC CONVERTER SC1631 January 29, 1998 APPLICATION EXAMPLES Figure 1. 3V Output Step-Up Converter Figure 2. 5V Output Step-Up Converter Figure 3. 1-Cell Input 3V Output Step-Up Converter © 1997 SEMTECH CORP. 652 MITCHELL ROAD NEWBURY PARK CA 91320 LOW VOLTAGE STEP-UP DC-DC CONVERTER SC1631 January 29, 1998 APPLICATION EXAMPLES (cont.) Figure 4. 1-Cell Input 5V Output Step-Up Converter Figure 5. 4-Cell Input Step-Up/Step-Down Converter Figure 6. Low Supply Current Burst Mode Step-Up Converter © 1997 SEMTECH CORP. 652 MITCHELL ROAD NEWBURY PARK CA 91320 LOW VOLTAGE STEP-UP DC-DC CONVERTER SC1631 January 29, 1998 DEVICE OUTLINE - SO-8 PIN DESCRIPTIONS PIN 1: ILIM/SD (1) Connected to VIN pin through a resistor to set the switch peak current. It serves to protect the IC and inductor, as well as to improve efficiency and output ripple. However, the supply capability of the SC1631 is limited by the current limit resistor (see typical performance characteristics). The ILIM/SD pin should be shorted to VIN if limiting switch peak current is not required. (2) The SC1631 goes into shutdown mode and consumes less than 10µA when the ILIM/SD pin is pulled to ground. PIN 2: VIN Input supply. PIN 3: SW Drain of the power switch, to be connected to the inductor and diode. PIN 5: CGND Ground for control circuits of the IC. It should be separated from SGND to avoid interference. PIN 6: LBO Open drain output of the battery low detector, with 45 Ohm “On Resistance” at VIN=2V. It is pulled low when the voltage on the LBI pin is below 1.22 volts. PIN 7: LBI The inverting input of the battery low detector, of which the non-inverting input is internally connected to the 1.22V voltage reference. PIN 8: VOUT The output voltage feeds back to the IC through this pin. PIN 4: SGND Ground connected to the source of the power switch. PIN CONFIGURATION © 1997 SEMTECH CORP. 652 MITCHELL ROAD NEWBURY PARK CA 91320