DC to DC Converter Control Circuit

Transcription

1 DC to DC Converter Control Circuit SMD34063 FEATURES Operation from 3.0V to 40V Input Low Standby Current Current Limiting Output Switch Current to.5a Output Voltage Adjustable Frequency Operation to 00kHz Precision 2% Reference DESCRIPTION The SMD34063 Series is a monolithic control circuit containing the primary functions required for DC-to-DC converters. These devices consist of an internal temperature compensated reference, comparator, controlled duty cycle oscillator with an active current limit circuit, driver and high current output switch. This series was specifically designed to be incorporated in Step-Down and Step-Up and voltage Inverting applications with a minimum number of external components. APPLICATIONS Chargers Adaptor Mother Board Scanner PACKAGE/ORDER INFORMATION Switch Collector Driver Collector Switch Emitter I PK Sense Order Part Number SMD34063MST Timing Capacitor Gnd V CC 8-Pin Plastic SOIC Surface Mount (Top View) Comparator Inverting Input Switch Collector Switch Emitter Timing Capacitor Driver Collector I PK Sense V CC SMD34063M Gnd 8-Pin Plastic DIP (Top View) Comparator Inverting Input - -

2 ABSOLUTE MAXIMUM RATINGS (Note ) Power Supply Voltage Comparator Input Voltage Range Switch Collector Voltage Switch Emitter Voltage (VPin = 40 V) Switch Collector to Emitter Voltage Driver Collector Voltage Driver Collector Current SMD V -0.3V < V < 40V 40V 40V 40V 40V 00mA Switch Current.5A Operating Ambient Temperature Range 0 C 70 C Storage Temperature Range Operating Junction Temperature 65 C to +50 C +50 C Note : Exceeding these ratings could cause damage to the device. All voltages are with respect to ground. Currents are positive into, negative out of the specified terminal. POWER DISSIPATION TABLE DIP 8 Package Power dissipation (P D ), T A = 25 C.3W Thermal Resistance-Junction to Ambient, θ JA 95 C /W SOIC 8 Package Power dissipation (P D ), T A = 25 C 757mW Thermal Resistance-Junction to Ambient, θ JA 65 C /W BLOCK DIAGRAM SC 8 DrC Q2 Q S Q 00 R SE 2 7 I SEN C T Isen Oscillator Cap 3.25V Reference 6 V CC Gnd 4 5 V FB - 2 -

3 TYPICAL APPLICATIONS 70uH L 8 80 Q Q2 Q S R C T Isen Oscillator 6 Rsc 0.22 V IN 2V.25V Reference 00uF 500pF 4 5 V OUT 28V/75mA 47K 330uF 2.2K Figure Step-Up Converter Application Circuits 8 Q Q2 Q S R 2 7 L 220uH N589 3 C T Oscillator Isen 6 Rsc 0.33 V IN 25V.25V Reference 00uF 470pF 4 5 V OUT 5V/500mA 3.6K 470uF.2K Figure 2 Step-Down Converter Application Circuits - 3 -

4 TYPICAL APPLICATIONS (Continued) 8 Q Q2 Q S R 2 7 L 88uH N pF 3 C T.25V Reference Ipk Oscillator 6 Rsc 0.24 V IN 4.5V to 6.0V 00uF 4 5 V OUT -2V/00mA 000uF K R2 R.2K 8.2K Figure 3 Voltage Inverting Converters - 4 -

5 TYPICAL APPLICATIONS (Design Reference Table) SMD34063 Calculation Step-Down Step-Up Voltage-Inverting t on /t off V out + V F V in(min) V sat V out V out + V F V in(min) V in(min) V sat V out + V F V in V sat t on + t off f f f t off t on + t off t on /t off + t on + t off t on /t off + t on + t off t on /t off + t on (t on + t off ) t off (t on + t off ) t off (t on + t off ) t off C T t on t on t on I pk(switch) 2I out(max) 2I out(max) (t on /t off + ) 2I out(max) (t on /t off + ) R SC 0.3/I pk(switch) 0.3/I pk(switch) 0.3/I pk(switch) I pk(switch) ) t on(max) ( (V in(min) V sat )) t on(max) L (min) ( (V in(min) V sat V out ) I pk(switch) ) t on(max) ( (V in(min) V sat ) I pk(switch) C O I pk(switch) ( t on + t off ) 8V ripple(pp) 9 I out t on V ripple(pp) 9 I out t on V ripple(pp) V F : Forward Voltage drop of the output rectifier V sat : Saturation voltage of the output switch. The following power supply characteristics must be chosen: V in - Nominal input voltage V out - Desired output voltage, V out =.25( + R/R2) I out - Desired output current. f min Minimum desired output switching frequency at the selected values of V in and I O V ripple(pp) Desired peak to peak output ripple voltage. Application concerns: To get the best regulation performance, Low ESR capacitors at Vout are suggested

6 ELECTRICAL CHARACTERISTICS Unless otherwise specified, these specifications apply VCC = 5.0 V, T A = 0 C to 70 C Parameter Test Conditions Min Typ Max Units Oscillator Frequency V Pin 5 = 0 V, C T =.0 nf, T A = 25 C KHz Charge Current V CC = 5.0V to 40V, T A = 25 C µa Discharge Current V CC = 5.0V to 40V, T A = 25 C µa Discharge to Charge Current Ration Current Limit Sense Voltage Output Switch (Note 4) Saturation Voltage (Darlington Connection, Note 5) Saturation Voltage (Darlington Connection Note 5) Pin 7 to V CC, T A = 25 C Ichg = Idschg, T A = 25 C mv I SW =.0A, Pins, 8 connected V I SW =.0A, R Pin 8 = 82Ω to V CC, Force β = 20 DC Current Gain I SW =.0A, V CE = 5.0V, T A = 25 C V Collector Off-State Current V CE = 40V µa Comparator Threshold Voltge T A = 25 C V Input Bias Current V IN = 0V na Total Device Supply Current V CC = 5.0V to 40V, C T =.0 nf, Pin 7 = V CC, V Pin 5 > V TH, Pin 2 = Gnd, remaining pins open 4.0 ma Note 4: Low duty cycle pulse techniques are used during test to maintain junction temperature as close to ambient temperature as possible. Note 5: If the output switch is driven into hard saturation (non Darlington configuration) at low switch currents ( 300 ma) and high driver currents ( 30 ma), it may take up to 2.0 ms for it to come out of saturation. This condition will shorten the off time at frequencies 30 khz, and is magnified at high temperatures. This condition does not occur with a Darlington configuration, since the output switch cannot saturate. If a non Darlington configuration is used, the following output drive condition is recommended: Forced β of output switch = I C output / ( IC driver 7.0 ma* ) 0 ( * The 00 W resistor in the emitter of the driver device requires about 7.0 ma before the output switch conducts.) - 6 -

7 CHARACTERIZATION CURVES VCE (SAT), SATURATION VOLTAGE(V) Emitter Follower Configuration Output Saturation Voltage versus Emitter Current I E, EMITTER CURRENT (A) VCE (SAT), SATURATION VOLTAGE(V) SMD34063 Common Emitter Configuration Output Switch Saturation Voltage versus Collector Current I C, COLLECTOR CURRENT (A) Current Limit Sense Voltage(V) Current Limit Sense Voltage Vs. Temperature ICC, Supply Current (ma) Standby Supply Current vs. Supply Voltage T A, Ambient Temperature ( C) V CC, Supply Voltage (V) Output Switch On Off Time vs. Oscillator Timing Capacitor Timing Capacitor Waveform Output Switch On-Off Teim(µS) Oscillator Voltage (V) C T, OSCILLATOR TIMING CAPACITOR (nf) 0µS/Div - 7 -

8 PACKAGE DESCRIPTION Dimensions in inches (millimeters) unless otherwise specified 8 Pin DIP / ( /- 0.27) ( ) 0.06 (.524) ( ) ( ) / (.43 +/- 0.83) / ( / ) ( ) / ( / ) J ( ) 95 +/- 5 8 Pin SOIC ( ) ( ) ( ) D ( ) (.270) TYP ( ) SEATING PLAN ( ) ( ) 8.0 MAX - 8 -

9 MARKING DIAGRAM DIP 8 SO M YYWW 34063MS YYWW YY = Year, WW = Working Week - 9 -

10 IMPORTANT NOTICE Shamrock Micro Devices (SMD) reserves the right to make changes to its products or to discontinue any integrated circuit product or service without notice, and advises its customers to obtain the latest version of relevant information to verify, before placing orders, that the information being relied on is current. A few applications using integrated circuit products may involve potential risks of death, personal injury, or severe property or environmental damage. SMD integrated circuit products are not designed, intended, authorized, or warranted to be suitable for use in life-support applications, devices or systems or other critical applications. Use of SMD products in such applications is understood to be fully at the risk of the customer. In order to minimize risks associated with the customer s applications, the customer should provide adequate design and operating safeguards