HIGH OUTPUT CURRENT CHARGE PUMP DOUBLER October 20, 2000 TEL:805-498-2111 FAX:805-498-3804 WEB:http://www.semtech.com DESCRIPTION The SC1462 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 SC1462 charge pump can be used for applications that require up to 80mA of output current with VIN = 2.5V to 5.5V. Typical dropout voltage (2*Vin-Vout) is shown below for several values of Vin. 0.9 Ou tpu t D ropou t Voltage (V) 0.7 0.6 FEATURES •= Input supply voltage range of 1.65V to 5.5V •= Small size - 6 pin SOT-23 package •= Typical efficiency of : •= •= •= •= •= •= 91% @ Vin = 2.5V, Iout = 45mA 94% @ Vin = 3.6V, Iout = 55mA Short circuit and over-temperature protection 140µA typical input current @ no load Shutdown current <1µA Designed to work with ceramic or Tantalum capacitors Fixed frequency of 160kHz All specifications rated over full temperature range (-40°C to 85°C) APPLICATIONS •= Cellular phones •= Handheld devices T ypical Dropou t Voltage vs Iou t @T a = 25 D eg. C . 0.8 SC1462 Vin = 1.5V Vin = 2.5V Vin = 3.6V Vin = 4.5V Vin = 5.5V ORDERING INFORMATION 0.5 (1) DEVICE 0.4 0.3 SC1462ISKTR PACKAGE Temp. Range (TA) SOT-23-6 -40°C to 85°C 0.2 0.1 0.0 000E+0 20E-3 40E-3 60E-3 80E-3 100E-3 Note: (1) Only available in tape and reel packaging. A reel contains 3000 devices. Iou t (A) TYPICAL APPLICATION SCHEMATIC 1 © 2000 SEMTECH CORP. 652 MITCHELL ROAD NEWBURY PARK CA 91320 HIGH OUTPUT CURRENT CHARGE PUMP DOUBLER October 20, 2000 SC1462 TEL:805-498-2111 FAX:805-498-3804 WEB:http://www.semtech.com ABSOLUTE MAXIMUM RATINGS Parameter Symbol Maximum Units Supply Voltage VIN -0.3 to +6.0 V Output Voltage VO -0.3 to +12 V VOUT Short Circuit Duration SC Indefinite Thermal Resistance Junction to Ambient θJA 230 °C/W Operating Ambient Temperature Range TA -40 to +85 °C Junction Temperature Range TJ -40 to +125 °C Storage Temperature Range TSTG -65 to +150 °C TL 300 °C Lead Temperature (Soldering) 10 seconds ELECTRICAL CHARACTERISTICS Unless specified: TA = -40°C to 85°C, SHDN = GND, 1.65V ≤ VIN ≤=5.5V, CIN = COUT = CBUCKET = 3.3µF (ESR = 0.3Ω). Parameter Symbol Input Supply Voltage VIN Input Supply Current IIN Conditions MIN TYP 1.65 MAX Units 5.5 V IO = 0, VIN = 2.5V freq = 160kHz 140 260 µA IO = 0, VIN = 3.6V freq = 160kHz 200 400 µA SHDN = VIN 0.1 1 µA Output Resistance(5) Rout VIN = 2.5V 9.5 13.5 Ω Output Resistance(5) Rout VIN = 3.6V 7.5 10.5 Ω Total Switch Resistance(6) RSW VIN = 2.5V 3 4.5 Ω Total Switch Resistance(6) RSW VIN = 3.6V 2 3 Ω IO VIN = 2.5V 80 mA VIN = 3.6V 80 mA 200 KHz Output Current Oscillator Frequency OSC 1.65V ≤ VIN ≤=5.5V Short Circuit Current ISC Vout = 0V 200 mA Output Ripple (pk-pk)(1)(3) VR IO = 45mA, VIN = 2.5V Frequency = 160kHz 75 mV Power Efficiency(1) η IO = 45mA,VIN = 2.5V freq = 160kHz 100 86 160 % 2 © 2000 SEMTECH CORP. 652 MITCHELL ROAD NEWBURY PARK CA 91320 HIGH OUTPUT CURRENT CHARGE PUMP DOUBLER October 20, 2000 SC1462 TEL:805-498-2111 FAX:805-498-3804 WEB:http://www.semtech.com ELECTRICAL CHARACTERISTICS Unless specified: TA = -40°C to 85°C, SHDN = GND, 1.65V ≤ VIN ≤=5.5V, CIN = COUT = CBUCKET = 3.3µF (ESR = 0.3Ω). Parameter Symbol Conditions VOUT IO = 0mA Input High Threshold Vih SHDN pin, 2.5 ≤ VIN ≤ 5.5 Input Low Threshold Vil SHDN pin, 2.5 ≤ VIN ≤ 5.5 Time to Regulation at Turn-on(2) tON IO = 0 to 60 mA, VIN = 3.6V freq = 160kHz (3) Maximum Output Voltage MIN TYP MAX Units 2*VIN V 1.6 V 0.4 V 500 µs Over Temperature protection(3) O.T. 140 °C Over Temperature Hysteresis(3) O.T.H 20 °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 200mA 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 Oscillator’s 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. This parameter was calculated from actual output resistance and the equation on page 7 for Rout . 3 © 2000 SEMTECH CORP. 652 MITCHELL ROAD NEWBURY PARK CA 91320 HIGH OUTPUT CURRENT CHARGE PUMP DOUBLER October 20, 2000 SC1462 TEL:805-498-2111 FAX:805-498-3804 WEB:http://www.semtech.com BLOCK DIAGRAM PIN CONFIGURATION (Top View) 6 Lead SOT-23 PIN DESCRIPTION Pin # SOT-23-6 Pin Name Pin Function 1 VIN Supply voltage input. 2 GND Ground. 3 C- 4 SHDN 5 VO Voltage output. 6 C+ This pin should be connected to the positive terminal of the external charging capacitor. 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. 4 © 2000 SEMTECH CORP. 652 MITCHELL ROAD NEWBURY PARK CA 91320 HIGH OUTPUT CURRENT CHARGE PUMP DOUBLER October 20, 2000 SC1462 TEL:805-498-2111 FAX:805-498-3804 WEB:http://www.semtech.com 5 Volts Fixed output Voltage U1 SC1462 VIN = 3V to 5.5V 1 VIN Vo U2 SC2982 5 1 2 4 Cin 3.3uF SHDN C+ GND C- 6 3 Cbucket Cout 3.3uF 3.3uF 3 VIN VOUT = 5V 5 VOUT GND EN 4 BYPASS C2 C3 1uF 10nF 2 EN 3.3 Volts Fixed output Voltage U1 SC1462 VIN = 2V to 3V 1 4 Cin 3.3uF VIN Vo SHDN C+ GND C2 U2 SC1453 5 1 6 3 3 Cbucket Cout 3.3uF 3.3uF EN IN OUT EN GND BYP 2 VOUT = 3.3V 5 4 C2 C3 1uF 10nF 5 © 2000 SEMTECH CORP. 652 MITCHELL ROAD NEWBURY PARK CA 91320 HIGH OUTPUT CURRENT CHARGE PUMP DOUBLER October 20, 2000 SC1462 TEL:805-498-2111 FAX:805-498-3804 WEB:http://www.semtech.com THEORY OF OPERATION OUTPUT CURRENT The SC1462 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. 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 7. Typical dropout voltages versus Iout are graphed on page 8. Charge transfer from Cin to C_charge ON S1,S2 OFF ON S3,S4 OFF Charge transfer from (Cin,and C_charge) to Cout S1 S4 C1+ C_charge THERMAL SHUTDOWN The thermal shutdown circuit provides added protection to the SC1462. 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 140°C. The charge pump is enabled only if the junction temperature drops to approximately 120°C. The SC1462 will cycle in and out of thermal shut down until the short circuit or the excessive load condition on Vout is removed, therby 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 * θJA Cout ; θJA = 230 °C/W C1- Vout S3 Vin S2 Cin Gnd Gnd 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. If VOUT is less than VIN - 200mV, then all switches are turned off and VOUT is charged with a 200mA current source from VIN. When VOUT reaches VIN - 200mV , the current source is disconnected from output and the charge pump circuitry is enabled again. 6 © 2000 SEMTECH CORP. 652 MITCHELL ROAD NEWBURY PARK CA 91320 HIGH OUTPUT CURRENT CHARGE PUMP DOUBLER October 20, 2000 SC1462 TEL:805-498-2111 FAX:805-498-3804 WEB:http://www.semtech.com CAPACITOR SELECTION LAYOUT CONSIDERATION Capacitor selection is based on both the maximum acceptable ripple voltage and the maximum tolerable drop at the output. Standard power board layout should 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 SC1462. 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. Vout_ripple Iout = + 2 x Iout x ESR_ C out 2 x Fosc x C out 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). Following tables show typical capacitor characteristics, and capacitor manufactures. Component ESR (Ohms) 0.1 uF Ceramic 0603 package 0.050 1.60 1.0 uF Ceramic 1206 package 0.040 0.47 10 uF Ceramic 1206 package 0.075 0.5 47 uF, 16V Tantalum D case 0.100 0.60 330 uF, 6.3V “OSCON” 0.025 2.5 330 uF, 16V Al Electrolytic 0.143 2.37 820 uF, 4.0V “OSCON” 0.012 2.5 1000 uF, 10V Al Electrolytic 0.053 5 Capacitor Manufacturers ESL (nH) Phone AVX Corp. (803)-448-9411 VISHAY (207)-324-4140 Nichicon Corp. (708)-843-7500 muRata (800)-831-9172 TOKIN (408)-432-8020 Taiyo Yuden (800)-348-2496 Sanyo (619)-661-6835 A good approximation for calculating the output resistance is shown below. R out ≅ 1 + 2 × R SW + 4 × ESR_ Cbucket + ESR_ C out Fosc x Cbucket 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. 7 © 2000 SEMTECH CORP. 652 MITCHELL ROAD NEWBURY PARK CA 91320 HIGH OUTPUT CURRENT CHARGE PUMP DOUBLER October 20, 2000 SC1462 TEL:805-498-2111 FAX:805-498-3804 WEB:http://www.semtech.com T ypical Dropou t Voltage vs Iou t @T a = 25 D eg. C . T ypical Iin vs Vin @T a = 25 Deg. C . 0.9 700E-6 Ou tpu t D ropou t Voltage (V) 600E-6 500E-6 Iin (A ) Vin = 1.5V 0.8 400E-6 300E-6 200E-6 100E-6 Vin = 2.5V Vin = 3.6V 0.7 Vin = 4.5V Vin = 5.5V 0.6 0.5 0.4 0.3 0.2 0.1 Io = 0mA 000E+0 0.0 1.0 2.0 3.0 4.0 5.0 6.0 000E+0 20E-3 40E-3 Vin (V) 80E-3 100E-3 T ypical D ropou t Voltage vs T a T ypical Iin vs T a @ Io = 0mA 550E-3 900E-6 Vin = 5.5V 800E-6 Vin = 2.5V, Iout = 50mA Ou tpu t Dropou t Voltage (V) Vin = 4.5V Vin = 3.6V 700E-6 Vin = 2.5V Vin = 1.5V 600E-6 Iin (A ) 60E-3 Iou t (A) 500E-6 400E-6 300E-6 200E-6 Vin = 3.6V, Iout = 60mA 500E-3 450E-3 400E-3 350E-3 100E-6 300E-3 000E+0 -40 -20 0 20 40 60 80 -40 -20 0 20 40 60 80 T a (Deg. C.) Ta (Deg. C.) T ypical Efficien cy vs Iou t @T a = 25 D eg. C . 100% Vout Ripple 50mV/Div. Efficien cy (%) 96% 92% 88% Vin = 5.5V Vin = 4.5V 84% Vin = 3.6V Iout = 60mA Cin = Cout = Cbucket =3.3uF Vin = 3.6V Vin = 2.5V Vin = 1.5V 80% 000E+0 20E-3 40E-3 60E-3 80E-3 100E-3 Iou t (A) 8 © 2000 SEMTECH CORP. 652 MITCHELL ROAD NEWBURY PARK CA 91320 HIGH OUTPUT CURRENT CHARGE PUMP DOUBLER October 20, 2000 SC1462 TEL:805-498-2111 FAX:805-498-3804 WEB:http://www.semtech.com DEVICE OUTLINE - SOT23-6L MINIMUM LAND PATTERN - SOT23-6L ECN00-1344 9 © 2000 SEMTECH CORP. 652 MITCHELL ROAD NEWBURY PARK CA 91320