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 quies-
cent 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 V
IN
= 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
K
Small size - 6 pin SOT-23 package
K
Typical efficiency of :
K
K
K
K
K
K
91% @ Vin = 2.5V, Iout = 15mA
Short circuit and over-temperature protection
55µA typical input current @ no load
Shutdown current <1µA
Designed to work with ceramic or Tantalum capacitors
Fixed frequency of 32kHz
All specifications rated over full temperature range
(-40°C to 85°C)
Applications
K
Cellular phones
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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
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POWER MANAGEMENT
Absolute Maximum Rating
Parameter
Supply Voltage
Output Voltage
V
OUT
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
θ
JA
T
A
T
J
T
STG
T
L
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:
T
A
= -40°C to 85°C, SHDN = GND, 1.65V
≤
V
IN
≤
5.5V, Frequency =32 kHz, C
IN
= C
OUT
= C
BUCKET
= 1.0µF (ESR = 0.3Ω).
Parameter
Input Supply Voltage
Input Supply Current
Symbol
V
IN
I
IN
I
O
= 0, V
IN
= 2.5V
I
O
= 0, V
IN
= 5.0V
SHDN = V
IN
Output Resistance
(5)
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
(1) (3)
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
µA
µA
µA
Ω
Ω
Ω
Ω
R
OUT
R
OUT
R
SW
R
SW
I
O
OSC
I
SC
V
R
η
V
out
V
IH
V
IL
V
IN
= 2.5V
V
IN
= 5.0V
V
IN
= 2.5V
V
IN
= 5.0V
V
IN
= 2.5V
22
V
OUT
= 0V
I
O
= 8mA, V
IN
= 2.5V
I
O
= 8mA, V
IN
= 2.5V
I
O
= 15mA, V
IN
= 5.0V
I
O
= 0mA
SHDN pin, 2.5V
≤
V
IN
≤
5.5V
SHDN pin, 2.5V
≤
V
IN
≤
5.5V
1.6
90
90
25
32
100
290
42
mA
KHz
mA
mV
%
%
2*V
in
0.4
V
V
V
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Electrical Characteristics (Cont.)
Unless specified:
T
A
= -40°C to 85°C, SHDN = GND, 1.65V
≤
V
IN
≤
5.5V, Frequency =32 kHz, C
IN
= C
OUT
= C
BUCKET
= 1.0µF (ESR = 0.3Ω).
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
I
O
= 0 to 15mA, V
IN
= 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
V
OUT
is less than
V
IN
- 200mV, then all switches are turned off and
V
OUT
is charged with a 100mA current source from
V
IN
. When
V
OUT
reaches
V
IN
- 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
R
OUT
. See the CAPACITOR SELECTION
section for information on applying the
R
OUT
specification.
(6) The parameter
R
SW
is equal to the total resistance of all 4 internal switches. See the CAPACITOR SELECTION section for information on applying
the
R
SW
specification. The parameter was calculated from actual output resistance and the equation on page 6 for
R
OUT
.
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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
C-
SHDN
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)
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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 V
OUT
is less than V
IN
- 200mV, then all switches are
turned off and V
OUT
is charged with a 100mA current source
from V
IN
. When V
OUT
reaches V
IN
- 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 calcu-
lation of the dropout voltage is given in the capacitor se-
lection 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 V
OUT
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 en-
abled only if the junction temperature drops to approxi-
mately 120°C. The SC1462A will cycle in and out of ther-
mal shut down until the short circuit or the excessive
load condition on Vout is removed, there by improving de-
vice 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.
T
J
= T
a
+ P
diss
*
θJA
;
θJA
= 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 pro-
tection against output short circuit and limits large cur-
rent spikes generated during the initial start up to charge
output capacitor.
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