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HIGH OUTPUT CURRENT CHARGE PUMP DOUBLER
October 20, 2000
SC1462
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.
T ypical Dropou t Voltage vs Iou t @T a = 25 D eg. C .
0.9 0.8
Vin = 1.5V Vin = 2.5V Vin = 3.6V Vin = 4.5V Vin = 5.5V
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 140A typical input current @ no load Shutdown current <1A Designed to work with ceramic or Tantalum capacitors Fixed frequency of 160kHz All specifications rated over full temperature range (-40C to 85C)
APPLICATIONS *= Cellular phones *= Handheld devices
Ou tpu t D ropou t Voltage (V)
0.7 0.6 0.5 0.4 0.3 0.2 0.1 0.0 000E+0
ORDERING INFORMATION
DEVICE
(1)
PACKAGE SOT-23-6
Temp. Range (TA) -40C to 85C
SC1462ISKTR
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 (c) 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 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, CIN = COUT = CBUCKET = 3.3F (ESR = 0.3).
Parameter Input Supply Voltage Input Supply Current
Symbol VIN IIN
Conditions
MIN 1.65
TYP
MAX 5.5
Units V A A A
IO = 0, VIN = 2.5V freq = 160kHz IO = 0, VIN = 3.6V freq = 160kHz SHDN = VIN
140 200 0.1 9.5 7.5 3 2
260 400 1 13.5 10.5 4.5 3 80 80
Output Resistance(5) Output Resistance(5) Total Switch Resistance(6) Total Switch Resistance(6) Output Current
Rout Rout RSW RSW IO
VIN = 2.5V VIN = 3.6V VIN = 2.5V VIN = 3.6V VIN = 2.5V VIN = 3.6V

mA mA KHz mA mV %
Oscillator Frequency Short Circuit Current Output Ripple (pk-pk)(1)(3) Power Efficiency(1)
OSC ISC VR
1.65V VIN =5.5V Vout = 0V IO = 45mA, VIN = 2.5V Frequency = 160kHz IO = 45mA,VIN = 2.5V freq = 160kHz
100
160 200 75
200
86
2 (c) 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 = -40C to 85C, SHDN = GND, 1.65V VIN =5.5V, CIN = COUT = CBUCKET = 3.3F (ESR = 0.3).
Parameter Maximum Output Voltage Input High Threshold Input Low Threshold Time to Regulation at Turn-on(2) Over Temperature protection(3) Over Temperature Hysteresis(3)
(3)
Symbol VOUT Vih Vil tON O.T. O.T.H
Conditions IO = 0mA SHDN pin, 2.5 VIN 5.5 SHDN pin, 2.5 VIN 5.5 IO = 0 to 60 mA, VIN = 3.6V freq = 160kHz
MIN
TYP
MAX 2*VIN
Units V V
1.6 0.4 500 140 20
V s 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 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 (c) 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 1 2 3 4 5 6 Pin Name VIN GND CSHDN VO C+ Pin Function 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. 4 (c) 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
VIN = 3V to 5.5V 1 4 Cin 3.3uF
U1 SC1462 VIN Vo 5 6 Cbucket 3 3.3uF Cout 3.3uF 3 1 2 SHDN C+ GND C2 VIN GND EN
U2 SC2982 VOUT 5
VOUT = 5V
BYPASS
4 C2 10nF C3 1uF
EN
3.3 Volts Fixed output Voltage
VIN = 2V to 3V 1 4 Cin 3.3uF
U1 SC1462 VIN Vo 5 6 Cbucket 3 3.3uF Cout 3.3uF EN 1 3 IN
U2 SC1453 OUT BYP 5 4
VOUT = 3.3V
SHDN C+ GND C2
EN GND 2
C2 10nF
C3 1uF
5 (c) 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
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.
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 7. Typical dropout voltages versus Iout are graphed on page 8.
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 140C. The charge pump is enabled only if the junction temperature drops to approximately 120C. 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 * JA JA = 230 C/W
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
C1+
C_charge
S4
Cout
;
C1-
Vout
S3
Vin
Gnd Cin
S2
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 (c) 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
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.
Vout_ripple Iout = + 2 x Iout x ESR_ C out 2 x Fosc x C out
LAYOUT CONSIDERATION
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. Following tables show typical capacitor characteristics, and capacitor manufactures. Component 0.1 uF Ceramic 0603 package 1.0 uF Ceramic 1206 package 10 uF Ceramic 1206 package 47 uF, 16V Tantalum D case 330 uF, 6.3V "OSCON" 330 uF, 16V Al Electrolytic 820 uF, 4.0V "OSCON" 1000 uF, 10V Al Electrolytic Capacitor Manufacturers AVX Corp. VISHAY ESR (Ohms) 0.050 0.040 0.075 0.100 0.025 0.143 0.012 0.053 Phone (803)-448-9411 (207)-324-4140 (708)-843-7500 (800)-831-9172 (408)-432-8020 (800)-348-2496 (619)-661-6835 ESL (nH) 1.60 0.47 0.5 0.60 2.5 2.37 2.5 5
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_ Cbucket + ESR_ C out Fosc x Cbucket
Nichicon Corp. muRata TOKIN Taiyo Yuden Sanyo
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 (c) 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 .
0.9
Vin = 1.5V Vin = 2.5V Vin = 3.6V Vin = 4.5V Vin = 5.5V
T ypical Iin vs Vin @T a = 25 Deg. C .
700E-6 600E-6 500E-6
0.8
Ou tpu t D ropou t Voltage (V)
Io = 0mA
0.7 0.6 0.5 0.4 0.3 0.2 0.1 0.0
Iin (A )
400E-6 300E-6 200E-6 100E-6 000E+0 1.0 2.0 3.0 4.0 5.0 6.0
000E+0
20E-3
40E-3
60E-3
80E-3
100E-3
Vin (V)
Iou t (A)
T ypical Iin vs T a @ Io = 0mA
900E-6
Vin = 5.5V
T ypical D ropou t Voltage vs T a
550E-3
800E-6 700E-6 600E-6
Vin = 3.6V Vin = 2.5V Vin = 1.5V
Ou tpu t Dropou t Voltage (V)
Vin = 4.5V
Vin = 2.5V, Iout = 50mA
500E-3
Vin = 3.6V, Iout = 60mA
450E-3
Iin (A )
500E-6 400E-6 300E-6 200E-6 100E-6 000E+0 -40 -20 0 20 40 60 80
400E-3
350E-3
300E-3 -40 -20 0 20 40 60 80
Ta (Deg. C.)
T a (Deg. C.)
T ypical Efficien cy vs Iou t @T a = 25 D eg. C .
100%
96%
Vout Ripple 50mV/Div.
Efficien cy (%)
92%
88%
Vin = 5.5V
84%
Vin = 4.5V Vin = 3.6V Vin = 2.5V Vin = 1.5V
80% 000E+0 20E-3 40E-3 60E-3 80E-3 100E-3
Vin = 3.6V Iout = 60mA Cin = Cout = Cbucket =3.3uF
Iou t (A)
8 (c) 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 (c) 2000 SEMTECH CORP. 652 MITCHELL ROAD NEWBURY PARK CA 91320

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