LOW VOLTAGE STEP-UP DC-DC CONVERTER January 29, 1998 SC1633 TEL:805-498-2111 FAX:805-498-3804 WEB:http://www.semtech.com DESCRIPTION The SC1633 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 83% can be easily achieved at 70mA 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. A switching rate of 120kHz reduces the inductor size inductors of 47µH to 150µH inductance are recommended for most applications. FEATURES • High efficiency 87% • Power-saving shutdown mode (7µA typical) • Internal 0.8A switch • 120kHz switching rate • Adjustable switch current limit • On-chip low battery detector APPLICATIONS • Pocket organizers • Electronic dictionaries • Cameras • Pagers • Bar code scanners • LCD displays • Battery backup supplies • Portable instruments ORDERING INFORMATION BLOCK DIAGRAM (1) DEVICE VOLTAGE PACKAGE SC1633CS SC1633-3CS SC1633-5CS 3.3V 3.0V 5.0V SO-8 Note: (1) Add suffix ‘TR’ for tape and reel. ABSOLUTE MAXIMUM RATINGS Parameter 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 PIN CONFIGURATION TYPICAL APPLICATION CIRCUIT © 1997 SEMTECH CORP. 652 MITCHELL ROAD NEWBURY PARK CA 91320 LOW VOLTAGE STEP-UP DC-DC CONVERTER SC1633 January 29, 1998 ELECTRICAL CHARACTERISTICS Unless otherwise specified, TA = 25°C, VIN = 3.0V Parameter VIN 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 SC1633/SC1633-3 SC1633-5 160 250 Input Voltage Min 1.8 Output Voltage SC1633 SC1633-3 SC1633-5 IL = 70mA 3.16 2.88 4.80 Shutdown Mode Current Shutdown Recovery Time 7 VIN=2.5V Efficiency SC1633/SC1633-3 SC1633-5 Line Regulation SC1633 SC1633-3 SC1633-5 VIN=2.0 - 3.3V VIN=2.0 - 3.0V VIN=2.2 - 4.5V Load Regulation SC1633/SC1633-3 SC1633-5 Oscillator Frequency LBI Pin Trip Point LBO “On Resistance” SW “On Resistance” SC1633/SC1633-3 SC1633-5 Typ VIN = 2V µA 15 µA IL=70mA 1.8 msec IL=70mA 87 86 % IL=40mA 0.6 0.6 0.5 %VOUT IL=1mA - 70mA 0.6 0.5 %VOUT 90 120 150 kHz 1.17 1.22 1.27 V 45 Ω 1.75 1.25 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 SC1633 January 29, 1998 TYPICAL PERFORMANCE CHARACTERISTICS © 1997 SEMTECH CORP. 652 MITCHELL ROAD NEWBURY PARK CA 91320 LOW VOLTAGE STEP-UP DC-DC CONVERTER SC1633 January 29, 1998 TYPICAL PERFORMANCE CHARACTERISTICS (cont.) APPLICATION EXAMPLES Figure 1. 3V Output Step-Up Converter © 1997 SEMTECH CORP. 652 MITCHELL ROAD NEWBURY PARK CA 91320 LOW VOLTAGE STEP-UP DC-DC CONVERTER SC1633 January 29, 1998 APPLICATION EXAMPLES (cont.) Figure 2. 5V Output Step-Up Converter Figure 3. 1-Cell Input 3V Output Step-Up Converter Figure 4. 4-Cell Input Step-Up/Step-Down Converter © 1997 SEMTECH CORP. 652 MITCHELL ROAD NEWBURY PARK CA 91320 LOW VOLTAGE STEP-UP DC-DC CONVERTER SC1633 January 29, 1998 APPLICATION EXAMPLES (cont.) Figure 5. 3-Cell Input 3V Output Step-Down Converter Figure 6. Boost-Drive 5V Output Step-Down Converter © 1997 SEMTECH CORP. 652 MITCHELL ROAD NEWBURY PARK CA 91320 LOW VOLTAGE STEP-UP DC-DC CONVERTER SC1633 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 SC1633 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 SC1633 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 CONFIGURATION PIN 4: SGND Ground connected to the source of the power switch. © 1997 SEMTECH CORP. 652 MITCHELL ROAD NEWBURY PARK CA 91320