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| High Efficiency Charge Pump Doubler POWER MANAGEMENT Description The SC1462A is a versatile charge pump designed for use in battery operated power supply applications over the wide input range of 1.65 to 5.5 volts. A simple, low quiescent current charge pump doubler can be implemented without costly inductors or capacitors. Internal MOSFETs and control circuitry eliminate the need for costly board space and design time. The small 6 lead SOT-23 package helps minimize board space. The SC1462A charge pump can be used for applications that require up to 25mA of output current with VIN = 2.5V to 5.5V. Typical dropout voltage (2*Vin)-Vout is shown on page 8 for several values of Vin. Typ ic a l D ro p ou t V ol ta ge v s Io u t @ T a = 2 5 De g . C . Vin = 1.5 V Vin = 2.5 V Vin = 3.6 V Vin = 4.5 V Vin = 5.5 V SC1462A Features K Input supply voltage range of 1.65V to 5.5V KSmall size - 6 pin SOT-23 package KTypical efficiency of : K K K K K K 91% @ Vin = 2.5V, Iout = 15mA Short circuit and over-temperature protection 55A typical input current @ no load Shutdown current <1A Designed to work with ceramic or Tantalum capacitors Fixed frequency of 32kHz All specifications rated over full temperature range (-40C to 85C) Applications K Cellular phones K Handheld devices K LCD display 8 0 0 .0 E -3 7 0 0 .0 E -3 Out pu t Dropo ut V olta ge (V) 6 0 0 .0 E -3 5 0 0 .0 E -3 4 0 0 .0 E -3 3 0 0 .0 E -3 2 0 0 .0 E -3 1 0 0 .0 E -3 0 00 .0 E + 0 0 00 E + 0 5 E -3 1 0 E -3 1 5 E -3 2 0 E -3 2 5 E -3 3 0 E -3 Io u t (A ) Typical Application Schematic SC1462A 1uF 1uF 1uF Revision 1/2001 1 www.semtech.com 5+"$ ) POWER MANAGEMENT Absolute Maximum Rating Parameter Supply Voltage Output Voltage VOUT Short Circuit Duration Thermal Resistance Junction to Ambient Operating Ambient Temperature Range Junction Temperature Range Storage Temperature Range Lead Temperature (Soldering) 10 seconds Symbol VIN VO SC JA TA TJ TSTG TL Maximum -0.3 to +6.0 -0.3 to +12 Indefinite 230 -40 to +85 -40 to +125 -65 to +150 300 C/W C C C C Units V V Electrical Characteristics Unless specified: TA = -40C to 85C, SHDN = GND, 1.65V VIN 5.5V, Frequency =32 kHz, CIN = COUT = CBUCKET = 1.0F (ESR = 0.3). Parameter Input Supply Voltage Input Supply Current Symbol VIN I IN IO = 0, VIN = 2.5V IO = 0, VIN = 5.0V SHDN = VIN Output Resistance (5) Conditions MIN 1.65 T YP 55 160 0.1 50 38 8.5 7.4 MAX 5.5 75 225 1 60 45 Units V A A A ROUT ROUT RSW RSW IO OSC ISC (1) (3) VIN = 2.5V VIN = 5.0V VIN = 2.5V VIN = 5.0V VIN = 2.5V 22 VOUT = 0V IO = 8mA, VIN = 2.5V IO = 8mA, VIN = 2.5V IO = 15mA, VIN = 5.0V IO = 0mA SHDN pin, 2.5V VIN 5.5V SHDN pin, 2.5V VIN 5.5V 1.6 90 90 Output Resistance(5) Total Switch Resistance(6) Total Switch Resistance (6) Output Current Oscillator Frequency Short Circuit Current Output ripple (pk-pk) Power Efficiency(1) Maximum Output Voltage(3) Input High Threshold Input Low Threshold 25 32 100 290 42 mA KHz mA mV % % VR Vout VIH VIL 2*Vin 0.4 V V V 2001 Semtech Corp. 2 www.semtech.com 5+"$ ) POWER MANAGEMENT Electrical Characteristics (Cont.) Unless specified: TA = -40C to 85C, SHDN = GND, 1.65V VIN 5.5V, Frequency =32 kHz, CIN = COUT = CBUCKET = 1.0F (ESR = 0.3). Parameter Time to Regulation at Turn on(2) Over Temperature Protection (3) Over Temperature Hysteresis (3) Symbol t ON O.T. O.T.H. Conditions IO = 0 to 15mA, VIN = 5.0V MIN T YP 350 140 20 MAX Units us C C NOTES: (1) All electrical characteristics are for the application circuit on page 1. (2) Soft start functionality is performed along with short circuit protection. If VOUT is less than VIN - 200mV, then all switches are turned off and VOUT is charged with a 100mA current source from VIN. When VOUT reaches VIN - 200mV all switches are enabled. (3) Guaranteed by design. (4) This device is ESD sensitive. Use of standard ESD handling precautions is required. (5) The internal switch resistance, the capacitor ESR and the oscillators switching frequency all contribute to ROUT. See the CAPACITOR SELECTION section for information on applying the ROUT specification. (6) The parameter RSW is equal to the total resistance of all 4 internal switches. See the CAPACITOR SELECTION section for information on applying the RSW specification. The parameter was calculated from actual output resistance and the equation on page 6 for ROUT. 2001 Semtech Corp. 3 www.semtech.com 5+"$ ) POWER MANAGEMENT Pin Configuration (TOP VIEW) Ordering Information Part Number(1) SC1462AISKTR Package SOT-23-6 Note: (1) Only available in tape and reel packaging. A reel contains 3000 devices. (6 Lead SOT-23) Pin Descriptions Pin # Pin Name Pin Function SOT -23-6 1 2 3 4 5 6 VIN GND CSHDN VO C+ Supply voltage input. Ground. This pin should be connected to the negative terminal of the external charging capacitor. Shutdown pin. When this pin is connected to VIN, the device enters sleep mode. Voltage output. This pin should be connected to the positive terminal of the external charging capacitor. Block Diagram Marking Information Top Mark 462A yyww Bottom Mark yyww = Datecode (Example : 9908) 2001 Semtech Corp. 4 www.semtech.com 5+"$ ) POWER MANAGEMENT Applications Information THEORY OF OPERATION The SC1462A utilizes a switched capacitor charge pump, to generate an output voltage approximately 2xVin. An internal oscillator generates two out of phase fixed frequency clock signals which turn on and off internal MOSFET switches. During phase1 of clock, the flying charge pump capacitor is charged to Vin through switches S1, and S2. During phase2 the flying charge pump capacitor is connected in series with the input voltage via S3, and S4, producing an output voltage. If VOUT is less than VIN - 200mV, then all switches are turned off and VOUT is charged with a 100mA current source from VIN. When VOUT reaches VIN - 200mV , the current source is disconnected from output and the charge pump circuitry is enabled again. OUTPUT CURRENT The dropout voltage for a charge pump doubler is defined as (2*Vin)-Vout. The maximum output current is usually specified as that which will not cause the dropout voltage to exceed the requirements of the application. The calculation of the dropout voltage is given in the capacitor selection section on page 6. Typical dropout voltages versus Iout are graphed on page 8. THERMAL SHUTDOWN The thermal shutdown circuit provides added protection to the SC1462A. During a VOUT short circuit condition or if the load is excessive , the over temperature circuitry will shut down the charge pump if the junction temperature exceeds approximately 140C. The charge pump is enabled only if the junction temperature drops to approximately 120C. The SC1462A will cycle in and out of thermal shut down until the short circuit or the excessive load condition on Vout is removed, there by improving device reliability. The junction temperature can be calculated from the following formula if the ambient temperature (Ta) and the charge pump power dissipation (Pdiss) are known. TJ = Ta + Pdiss * JA ; JA = 230 C/W Charge transfer from Cin to Cbucket ON S1,S2 OFF ON S3,S4 OFF Charge transfer from: Cin and Cbucket to Cout (Doubler) S1 1 2 1 S4 2 Vout = 2 x Vin Cout Cbucket Vin Cin S3 1 2 1 S2 2 Doubler SHORT CIRCUIT / SOFT START An internal current limit and soft start circuit provides protection against output short circuit and limits large current spikes generated during the initial start up to charge output capacitor. 2001 Semtech Corp. 5 www.semtech.com 5+"$ ) POWER MANAGEMENT Applications Information (Cont.) CAPACITOR SELECTION Capacitor selection is based on both the maximum acceptable ripple voltage and the maximum tolerable drop at the output. Ripple The peak to peak output ripple voltage is dependent on the following factors: 1- Oscillator Frequency 2- ESR of COUT 3- Capacitance value of Cout Item 1 is fixed and depend on the charge pump device used. Item 2, and 3 can be optimized for best performance and reduction of the output ripple. The following formula could be used for an approximation for Vout_ripple. Vou t_ripp le= Iou t + 2 x Iou t x ESR_ C ou t 2 x Fosc x C ou t This equation can be used to calculate Cbucket for a specific Vout when Vin and Iout are known. The maximum value for the Rsw from the Electrical Characteristics section on page 2 should be used in order to find a worst case number. LAYOUT CONSIDERATION Standard power board layout should be followed to ensure proper operation. Any stray inductance should be minimized, this can be achieved by using large power planes or traces, and reducing the distances between input, output and the load. All components should be placed as close as possible to the SC1462A. Following tables show typical capacitor characteristics, and capacitor manufactures. Component 0.1uF Ceramic 0603 Package 1.0uF Ceramic 1206 Package 10uF Ceramic 1206 Package 47uF,16V Tantalum D case 330uF,6.3V "OSCON" 330uF,16V Al. Electrolytic 820uF,4V "OSCON" 1000uF,10V Al. Electrolytic ESR() ) 0.050 0.040 0.075 0.100 0.025 0.143 0.012 0.053 ESL(nH) 1.60 0.47 0.50 0.60 2.50 2.37 2.50 5.00 Vout Drop The voltage drop at the output is specified with the following equation: Vout_drop = Iout * Rout Rout is dependent on the following factors: 1- Oscillator Frequency 2- ESR of COUT & Cbucket 3- Capacitance value of COUT & Cbucket 4- Internal switch resistance (Rsw = Total of all 4 switch resistances). A good approximation for calculating the output resistance is shown below. R out 1 + 2 x R SW + 4 x ESR_ C bucket + ESR_ C out Fosc x C bucket Capacitor Manufacturers AVX Corp. VISHAY Nichicon Corp. muRata TOKIN Taiyo Yuden Sanyo Phone (803) 448-9411 (207) 324-4140 (708) 843-7500 (800) 831-9172 (408) 432-8020 (800) 348-2496 (619) 661-6835 2001 Semtech Corp. 6 www.semtech.com 5+"$ ) POWER MANAGEMENT Applications Information (Cont.) VIN = 3V to 5.5V 1 4 U1 SC1462A VIN Vo 5 6 3 1 2 Cbucket 1.0uF Cout 1.0uF 3 U2 SC2982 VIN GND EN BYPASS VOUT 5 VOUT = 5V Cin 1.0uF SHDN C+ GND C2 4 C2 10nF C3 1uF 5 Volts Fixed output Voltage EN VIN = 2V to 3V 1 4 U1 SC1462A VIN Vo 5 6 3 1 3 U2 SC1453 IN EN GND 2 OUT BYP 5 4 VOUT = 3.3V Cin 1.0uF SHDN C+ GND C2 Cbucket 1.0uF Cout 1.0uF EN C2 10nF C3 1uF 3.3 Volts Fixed output Voltage 2001 Semtech Corp. 7 www.semtech.com 5+"$ ) POWER MANAGEMENT Typical Characteristics T ypi cal Iin v s V in @ T a = 25 D eg . C . 8 0 0 .0 E -3 1 8 0 E -6 7 0 0 .0 E -3 Typ ic a l D ro p ou t V ol ta ge v s Io u t @ T a = 2 5 De g . C . Vin = 1.5 V Vin = 2.5 V Vin = 3.6 V Vin = 4.5 V Vin = 5.5 V Out pu t Dropo ut V olta ge (V) Io = 0mA 1 6 0 E -6 1 4 0 E -6 1 2 0 E -6 6 0 0 .0 E -3 5 0 0 .0 E -3 4 0 0 .0 E -3 3 0 0 .0 E -3 2 0 0 .0 E -3 1 0 0 .0 E -3 0 00 .0 E + 0 Ii n (A ) 1 0 0 E -6 8 0 E -6 6 0 E -6 4 0 E -6 2 0 E -6 0 00 E + 0 1 .0 2 .0 3 .0 4 .0 5 .0 6 .0 0 00 E + 0 5 E -3 1 0 E -3 1 5 E -3 2 0 E -3 2 5 E -3 3 0 E -3 V i n (V ) Io u t (A ) Typical Iin vs Vin Io = 0mA T ypi c a l Iin v s T a @ Io = 0 mA 2 5 0E -6 Vin = 5. 5V Vin = 4. 5V Typical Dropout vs Iout T yp ic a l D r opo u t V o lta ge v s T a 6 0 0 E -3 5 5 0 E -3 V in = 2 .5 V , Iou t = 1 0mA V in = 5 .5 V , Iou t = 1 5mA 2 00E -6 Vin = 2. 5V Vin = 1. 5V O u tpu t Drop ou t V o lt ag e (V) Vin = 3. 6V 5 0 0 E -3 4 5 0 E -3 4 0 0 E -3 3 5 0 E -3 3 0 0 E -3 2 5 0 E -3 2 0 0 E -3 1 5 0E -6 Ii n (A) 1 00E -6 5 0E -6 0 00 E + 0 -4 0 -2 0 0 20 40 60 80 -4 0 -2 0 0 20 40 60 80 T a ( D e g . C .) T a (D e g. C .) Typical Iin vs Ta Io = 0mA T yp ic a l E ff ic i e nc y v s Io u t @ T a = 2 5 D eg . C . 1 00 % Typical Dropout vs Ta 96 % Vout Ripple 100mV/Div. Eff ic ie ncy (%) 92 % 88 % Vin = 5. 5V Vin = 4. 5V Vin = 3. 6V Vin = 2. 5V Vin = 1. 5V 84 % 80 % 3 E -3 8 E -3 1 3E -3 1 8E -3 2 3E -3 2 8E -3 Io ut (A ) Vin = 2.5V Iout = 8mA Cin = Cout = Cbucket = 1.0uF Typical Efficiency vs Iout 2001 Semtech Corp. 8 Typical Output Ripple www.semtech.com 5+"$ ) POWER MANAGEMENT Outline Drawing - SOT-23-6L Land Pattern - SOT-23-6L Contact Information Semtech Corporation Power Management Products Division 652 Mitchell Rd., Newbury Park, CA 91320 Phone: (805)498-2111 FAX (805)498-3804 2001 Semtech Corp. 9 www.semtech.com |
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