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| 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. A switching rate of 120kHz reduces the inductor size inductors of 25H to 50H are recommended for most applications. FEATURES * High efficiency 90% * Power-saving shutdown mode (7A typical) * Internal 2A switch * 120kHz switching rate * Adjustable switch current limit * On-chip low battery detector APPLICATIONS * Palmtop and notebook computers * Pocket organizers * Cameras * Pagers * Battery backup supplies * Portable instruments BLOCK DIAGRAM ORDERING INFORMATION DEVICE (1) OUTPUT VOLTAGE 3.3V 3.0V 5.0V PACKAGE SO-8 SC1631CS SC1631-3CS SC1631-5CS Note: (1) Add suffix `TR' for tape and reel. PIN CONFIGURATION ABSOLUTE MAXIMUM RATINGS Parameter Supply Voltage Operating Temperature Range Storage Temperature Range Symbol Maximum VIN TA TSTG 7.0 0 to 70 -65 to 125 Units V C C (c) 1997 SEMTECH CORP. 652 MITCHELL ROAD NEWBURY PARK CA 91320 LOW VOLTAGE STEP-UP DC-DC CONVERTER January 29, 1998 SC1631 ELECTRICAL CHARACTERISTICS Unless otherwise specified, TA = 25C, VIN = 3.0V Test Conditions Parameter Input Voltage Output Voltage SC1631 SC1631-3 SC1631-5 Switch Off Current No Load Current SC1631/SC1631-3 SC1631-5 Shutdown Mode Current Recovery Time from Shutdown Efficiency SC1631/SC1631-3 SC1631-5 Line Regulation SC1631 SC1631-3 SC1631-5 Load Regulation SC1631/SC1631-3 SC1631-5 Oscillator Frequency LBI Pin Trip Point LBO "On Resistance" SW "On Resistance" SC1631/SC1631-3 SC1631-5 SW Off Leakage Input Pin Bias Current Output Pin Leakage VIN = 2V VIN=1.8 - 3.3V VIN=1.8 - 3.0V VIN=2.2 - 3.3V VIN=2.5V IL=200mA IL=200mA VIN IL Min 1.5 3.16 2.88 4.80 3.30 3.00 5.00 105 160 180 7 0.4 87 90 0.6 0.5 0.8 0.3 0.8 90 1.17 120 1.22 45 0.5 0.4 1 10 10 150 1.27 15 Test Limits Typ Max 7.0 3.44 3.12 5.20 140 Units V V IL = 200mA A A A ms % IL=100mA %VOUT IL=10mA - 300mA %VOUT kHz V A nA/Pin nA/Pin (c) 1997 SEMTECH CORP. 652 MITCHELL ROAD NEWBURY PARK CA 91320 LOW VOLTAGE STEP-UP DC-DC CONVERTER January 29, 1998 SC1631 TYPICAL PERFORMANCE CHARACTERISTICS (c) 1997 SEMTECH CORP. 652 MITCHELL ROAD NEWBURY PARK CA 91320 LOW VOLTAGE STEP-UP DC-DC CONVERTER January 29, 1998 SC1631 TYPICAL PERFORMANCE CHARACTERISTICS (cont.) TYPICAL APPLICATION CIRCUIT (c) 1997 SEMTECH CORP. 652 MITCHELL ROAD NEWBURY PARK CA 91320 LOW VOLTAGE STEP-UP DC-DC CONVERTER January 29, 1998 SC1631 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 (c) 1997 SEMTECH CORP. 652 MITCHELL ROAD NEWBURY PARK CA 91320 LOW VOLTAGE STEP-UP DC-DC CONVERTER January 29, 1998 SC1631 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 (c) 1997 SEMTECH CORP. 652 MITCHELL ROAD NEWBURY PARK CA 91320 LOW VOLTAGE STEP-UP DC-DC CONVERTER January 29, 1998 SC1631 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 10A when the ILIM/SD pin is pulled to ground. PIN 2: VIN PIN 3: SW Input supply. 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. The inverting input of the battery low detector, of which the non-inverting input is internally connected to the 1.22V voltage reference. The output voltage feeds back to the IC through this pin. PIN 7: LBI PIN 8: VOUT PIN 4: SGND Ground connected to the source of the power switch. PIN CONFIGURATION (c) 1997 SEMTECH CORP. 652 MITCHELL ROAD NEWBURY PARK CA 91320 |
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