SEMTECH SC1462ISKTR

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