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LOW VOLTAGE MULTI-MODE DC-DC CONVERTER January 30, 1998 SC1630 TEL:805-498-2111 FAX:805-498-3804 WEB:http://www.semtech.com DESCRIPTION The SC1630 is a DC-DC converter designed to drive an external power switch for more flexibility, especially in higher voltage and larger power applications. Typically six components are required to set up a step-up configuration easily achieving an efficiency beyond 80%. A few more components are required to set up a step down configuration delivering 4A load current with 83% typical efficiency, 86% at 2A load, and 300A quiescent current. The output voltage can be internally set to 5V or externally set to an arbitrary value below breakdown voltage of the power switch. Logic-controlled shutdown mode is provided for power-saving. The low battery detector can also be configured as a linear regulator. A 120kHz switching rate reduces the inductor size. Inductors of 25H to 50H inductance are recommended for most applications. FEATURES * Default +5V output voltage * Adjustable output voltage with two resistors * Power-saving shutdown mode (7A typical) * 120kHz switching rate * On-chip low battery detector BLOCK DIAGRAM APPLICATIONS * Palmtop and notebook computers * Battery charger supply * Cellular telephones * LCD contrast supply * Flash memory programmer * Battery backup supplies * Portable instruments PIN CONFIGURATION ORDERING INFORMATION DEVICE (1) PACKAGE SO-8 SC1630CS Note: (1) Add suffix `TR' for tape and reel. ABSOLUTE MAXIMUM RATINGS Parameter Supply Voltage Operating Temperature Range Storage Temperature Range Symbol VIN TA TSTG Maximum 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 MULTI-MODE DC-DC CONVERTER January 30, 1998 SC1630 ELECTRICAL CHARACTERISTICS Unless otherwise specified, TA = 25C, VIN = 3.0V Parameter Input Voltage Default Output Voltage Switch Off Current Shutdown Mode Current Recovery Time from Shutdown Efficiency Line Regulation Load Regulation Oscillator Frequency LBI Pin Trip Point EXT Pin Driving Capabilities Pin 8 = 5V, Pin 3 = 0.85V Sourcing Sinking VIN = 2V VIN = 2.5V,IL = 200mA IL = 300mA (5V Output Step-Up Converter) VIN = 2.2 - 3.3V VOUT = 5V, IL = 100mA IL = 10mA - 500mA VOUT = 5V 90 IL = 200mA Conditions Min 1.8 4.80 5.00 105 7 0.4 85 0.6 2.5 120 1.22 80 50 45 10 10 150 Typ Max 7.0 5.20 140 15 Units V V A A ms % %VOUT %VOUT kHz V mA mA nA/Pin nA/Pin LBO "ON Resistance" Input Pin Bias Current Output Pin Leakage TYPICAL APPLICATIONS (c) 1997 SEMTECH CORP. 652 MITCHELL ROAD NEWBURY PARK CA 91320 LOW VOLTAGE MULTI-MODE DC-DC CONVERTER January 30, 1998 SC1630 TYPICAL APPLICATIONS (cont.) 5V Output Step-Up Converter 12V Output Step-Up Converter for Flash Memory 36V Output Step-Up Converter for Color LCD (c) 1997 SEMTECH CORP. 652 MITCHELL ROAD NEWBURY PARK CA 91320 LOW VOLTAGE MULTI-MODE DC-DC CONVERTER January 30, 1998 SC1630 TYPICAL APPLICATIONS (cont.) -24V Output Inverting Converter for LCD 2V Input 20mA Load -24V Output Inverting Converter for LCD 12V Dual Output Converter for Computer Interfacing (c) 1997 SEMTECH CORP. 652 MITCHELL ROAD NEWBURY PARK CA 91320 LOW VOLTAGE MULTI-MODE DC-DC CONVERTER January 30, 1998 SC1630 TYPICAL APPLICATIONS (cont.) 5V Output Step-Down Converter - 1 5V Output Step-Down Converter - 2 (c) 1997 SEMTECH CORP. 652 MITCHELL ROAD NEWBURY PARK CA 91320 LOW VOLTAGE MULTI-MODE DC-DC CONVERTER January 30, 1998 SC1630 TYPICAL APPLICATIONS (cont.) Step-Up Rechargeable Battery Charger * * * Charging current =0.8A, Auto Cut-Off at 0.25% -Delta-V point and fault conditions (RIF sets the charging current). VDD must be lower than VBAT. Short circuit condition is protected with a 2A fuse. Step-Up/Step-Down Rechargeable Battery Charger * * * * Fast charge current =0.8A when VDD TYPICAL PERFORMANCE CHARACTERISTICS (c) 1997 SEMTECH CORP. 652 MITCHELL ROAD NEWBURY PARK CA 91320 LOW VOLTAGE MULTI-MODE DC-DC CONVERTER January 30, 1998 SC1630 TYPICAL PERFORMANCE CHARACTERISTICS (cont.) (c) 1997 SEMTECH CORP. 652 MITCHELL ROAD NEWBURY PARK CA 91320 LOW VOLTAGE MULTI-MODE DC-DC CONVERTER January 30, 1998 SC1630 DEVICE OUTLINE - SO-8 PIN DESCRIPTIONS PIN 1: SD The SC1630 goes into shutdown mode and consumes less than 10A when the SD pin is pulled to ground, and it goes into normal operating mode when the SD pin is pulled to a positive voltage above 100mV. Input supply. Push-Pull driver output to drive external power switch. PIN 8: VOUT PIN 4: GND PIN 5: FB Ground. The output voltage can either be internally set to 5 volts by grounding the FB pin, or it can be externally set to an arbitrary voltage by applying to the FB pin the divider voltage of two external divider resistors. VOUT voltage is given by the following equation: PIN 6: LBO Open drain output of the battery low detector, with 45 Ohm "On Resis tance" at VIN=2V. It is pulled low when the voltage on 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 for internally set 5V operation. If the output voltage is externally set, the VOUT pin can be tied to any low impedance node with voltage between the external power switch threshold and 7 volts. PIN 7: LBI PIN 2: VIN PIN 3: EXT V OUT Where: R = 0 . 611 1 + 1 R2 PIN CONFIGURATION R1= Resistor connected beween FB Pin and VOUT pin. R2= Resistor connected between FB Pin and ground. VOUT = Output voltage to be set. (c) 1997 SEMTECH CORP. 652 MITCHELL ROAD NEWBURY PARK CA 91320 |
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