SC1101 SEMTECH | Alldatasheet

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Technical content

© 2000 SEMTECH CORP. 652 MITCHELL ROAD NEWBURY PARK CA 91320 VOLTAGE MODE PWM CONTROLLER February 29, 2000 BLOCK DIAGRAM Pentium is a registered trademark of Intel Corporation PIN CONFIGURATION 4 5 BST DH GND GND Vcc Cs(+) Cs(-) FB Top View (8 LEAD PLASTIC SOIC)

DESCRIPTION

The SC1101 is a versatile, low-cost, voltage-mode PWM controller designed for use in single ended DC/ DC power supply applications. A simple, fixed-voltage buck regulator can be implemented using the SC1101 with a minimum of external components. Internal level shift and drive circuitry eliminates the need for an ex- pensive p-channel, high-side switch. The small device footprint allows for compact circuit design. SC1101 features include a temperature compensated voltage reference, triangle wave oscillator, current limit comparator, frequency shift over-current protection, and an internally compensated error amplifier. Pulse by pulse current limiting is implemented by sensing the differential voltage across an external resistor, or an appropriately sized PC board trace. The SC1101 operates at a fixed frequency of 200kHz, providing an optimum compromise between efficiency, external component size, and cost.

FEATURES

  • Low cost / small size
  • Switch mode efficiency (90%)
  • 1% reference voltage accuracy
  • Over current protection
  • 500mA output drive
  • SO-8 package

APPLICATIONS

Pentium® P55 Core Supply

  • Low Cost Microprocessor Supplies
  • Peripheral Card Supplies
  • Industrial Power Supplies
  • High Density DC/DC Conversion TEL:805-498-2111 FAX:805-498-3804 WEB:http://www.semtech.com

ORDERING INFORMATION

(1) PACKAGE TEMP RANGE (T J) SC1101CS SO-8 0° to 125°C Note: (1) Add suffix ‘TR’ for tape and reel.

© 2000 SEMTECH CORP. 652 MITCHELL ROAD NEWBURY PARK CA 91320 VOLTAGE MODE PWM CONTROLLER February 29, 2000 Pin # Pin Name Pin Function 1V CC Device Input Voltage 2C s(-) Current Sense Input (Negative) 3C s(+) Current Sense Input (Positive) 4P GND Device Power Ground

5 DH High Side Driver Output

6 BST High Side Driver V

CC (Boost)

7 FB Error Amplifier Input (-)

8 GND Small Signal Ground

Parameter Symbol Maximum Units Input Voltage V CC to GND -0.3 to +7 V Ground Differential P GND to GND ± 1 V Boost Input Voltage BST to GND -0.3 to +15 V Operating Temperature T A 0 to +70 °C Storage Temperature T J -45 to +125 °C Lead Temperature (Soldering) 10 seconds T L 300 °C Thermal Resistance, Junction to Ambient θ JA 165 °C/W Thermal Resistance, Junction to Case θ JC 40 °C/W PIN DESCRIPTION ABSOLUTE MAXIMUM RATINGS

© 2000 SEMTECH CORP. 652 MITCHELL ROAD NEWBURY PARK CA 91320 VOLTAGE MODE PWM CONTROLLER February 29, 2000 TEST CIRCUIT VOUT=1.25*(R3+R4)/R4 +5V +12V VOUT 0.1uF 0.1uF BUK556 4uH 2.32k 1.00k 5mOhm PSR16C30CT C11 0.1uF C10 0.1uF SC1101CS GND 8VCC1 CS(-)2 CS(+)3 PGND4 DH 5 BST 6 FB 7 See Table See Table 1500uF 1500uF 1500uF 1500uF 1500uF 1500uF 1500uF J1 J2 VOUT R3 R4 3.45 174 100 3.30 165 100 3.10 147 100 2.90 133 100 2.80 124 100 2.50 100 100 1.50 20 100

ELECTRICAL CHARACTERISTICS

VCC = 4.75V to 5.25V; GND = PGND = 0V; VO = 3.3V; TA = 25°C; BST = 12V; Output current = 2A. Per test circuit, unless otherwise specified. PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS Reference V REF 1.238 1.250 1.263 V Over Temp 1.225 1.250 1.275 V Feedback Bias Current I FB 2.0 8.0 uA Quiescent Current I Q Current into VCC pin 5.0 8.0 mA Regulation Load REG LOAD IO=1A to 12A 0.5 1.0 % Regulation Line REG LINE 0.5 % Current Limit Threshold CLT CS(+) to CS(-) 60 70 80 mV Oscillator Frequency OSC 180 200 220 kHz Oscillator Frequency Shift OFS V FB < VREF/2 50 kHz Max Duty Cycle d.c. 90 95 % DH Sink/Source Current I O VBST - VDH = 4.5V (VDH - VPGND = 2V) 500 mA UVLO Threshold V UVLO 3.8 V

© 2000 SEMTECH CORP. 652 MITCHELL ROAD NEWBURY PARK CA 91320 VOLTAGE MODE PWM CONTROLLER February 29, 2000 Fig.3: Ripple; Vo=2.90V; Io=10A Fig.4: Efficiency 70% 75% 80% 85% 90% 95% 100% Output Current (Amps) Efficiency 3.50V Set 3.00V Set 2.40V Set 2.00V Set Fig.2: Load Regulation Characteristic -0.02 -0.01 0.01 0.02 0.03 0.04 0.05 Output Current (Amps) Voltage change (V) normalized to 0 at Io=2A -10 Frequency (Hz) Gain (dB) -45 135 180 Phase (deg) Gain Phase Fig.1: Error Amplifier, Gain and Phase

© 2000 SEMTECH CORP. 652 MITCHELL ROAD NEWBURY PARK CA 91320 VOLTAGE MODE PWM CONTROLLER February 29, 2000 LAYOUT GUIDELINES Careful attention to layout requirements are necessary for successful implementation of the SC1101 PWM con- troller. High currents switching at 200kHz are present in the application and their effect on ground plane voltage differentials must be understood and minimized. 1). The high power parts of the circuit should be laid out first. A ground plane should be used, the number and position of ground plane interruptions should be such as to not unnecessarily compromise ground plane integrity. Isolated or semi-isolated areas of the ground plane may be deliberately introduced to constrain ground currents to particular areas, for example the input capacitor and bottom Schottky ground. 2). The loop formed by the Input Capacitor(s) (Cin), the Top FET (Q1) and the Schottky (D1) must be kept as small as possible. This loop contains all the high current, fast transition switching. Connections should be as wide and as short as possible to minimize loop inductance. Minimizing this loop area will reduce EMI, lower ground injection currents, resulting in electrically “cleaner” grounds for the rest of the system and minimize source ringing, resulting in more reliable gate switching signals. 3). The connection between the junction of Q1, D1 and the output inductor should be a wide trace or copper re- gion. It should be as short as practical. Since this con- nection has fast voltage transitions, keeping this connec- tion short will minimize EMI. The connection between the output inductor and the sense resistor should be a wide trace or copper area, there are no fast voltage or current transitions in this connection and length is not so impor- tant, however adding unnecessary impedance will re- duce efficiency. 4) The Output Capacitor(s) (Cout) should be located as close to the load as possible, fast transient load currents are supplied by Cout only, and connections between Cout and the load must be short, wide copper areas to minimize inductance and resistance. 5) The SC1101 is best placed over an isolated ground plane area. GND and PGND should be returned to this isolated ground. This isolated ground area should be connected to the main ground by a trace that runs from the GND pin to the ground side of (one of) the output ca- pacitor(s). If this is not possible, the GND pin may be connected to the ground path between the Output Ca- pacitor(s) and the Cin, Q1, D1 loop. Under no circum- stances should GND be returned to a ground inside the Cin, Q1, D1 loop. 6) Vcc for the SC1101 should be supplied from the 5V supply through a 10Ω resistor, the Vcc pin should be de- coupled directly to GND by a 0.1µF ceramic capacitor, trace lengths should be as short as possible. Vout 4uH 5mOhm Cout +Cin 0.1uF 2.32k 1.00kQ1 0.1uF 12V IN Heavy lines indicate high current paths. SC1101CS GND 8VCC1 CS(-)2 CS(+)3 PGND4 DH 5 BST 6 FB 7 Rb Ra Fig. 5 Layout diagram for the SC1101

© 2000 SEMTECH CORP. 652 MITCHELL ROAD NEWBURY PARK CA 91320 VOLTAGE MODE PWM CONTROLLER February 29, 2000 7) The Current Sense resistor and the divider across it should form as small a loop as possible, the traces run- ning back to CS(+) and CS(-) on the SC1101 should run parallel and close to each other. The 0.1µF capacitor should be mounted as close to the CS(+) and CS(-) pins as possible. 8) To minimize noise pickup at the sensitive FB pin, the feedback resistors should both be close to the SC1101 with the bottom resistor (Rb) returned to ground at the GND pin. Under Voltage Lockout The under voltage lockout circuit of the SC1101 assures that the high-side MOSFET driver outputs remain in the off state whenever the supply voltage drops below set parameters. Lockout occurs if V CC falls below 3.8V. Nor- mal operation resumes once VCC rises above 3.8V. C2-C7 - AVX: TPSE227M010S0100 Q1, D1 - International Rectifier L1- Coilcraft: DO5022P-392HC +3.3V +12V GND VOUT +5V 0.1uF 6mOhm 0.1uF C10 0.1uF 220uF Cx 0.01 0.1uF 0.1uF SC1101CS GND 8VCC1 CS(-)2 CS(+)3 PGND4 DH 5 BST 6 FB 7 124 220uF 220uF 220uF IRL2203S 32CTQ030S C7 0.01uF Fig. 6: GTL+ 3.3V to 1.5V 8A Application TYPICAL APPLICATIONS

© 2000 SEMTECH CORP. 652 MITCHELL ROAD NEWBURY PARK CA 91320 VOLTAGE MODE PWM CONTROLLER February 29, 2000 C2-C7 - AVX: TPSE227M01S0100 Q1, D1 - International Rectifier L1 - Coilcraft: DO5022P-392HC +5V GND +3.3V 0.1uF 0.012 0.1uF C10 0.1uF 220uF 205 0.1uF SC1101CS GND 8VCC1 CS(-)2 CS(+)3 PGND4 DH 5 BST 6 FB 7 124 220uF + 220uF 220uF 220uF IRL2203S 32CTQ030 0.1uF LL42 1k Cx 0.01 Fig. 7: 5V to 3.3V 8A Application with flying capacitor boost TYPICAL APPLICATIONS (cont.)

© 2000 SEMTECH CORP. 652 MITCHELL ROAD NEWBURY PARK CA 91320 VOLTAGE MODE PWM CONTROLLER February 29, 2000 OUTLINE DRAWING JEDEC REF: MS-012AA LAND PATTERN SO-8 ECN00-900