Semiconductor Components Industries, LLC, 2002
January, 2002 Rev. 4
1
Publication Order Number:
NCP1400A/D
NCP1400A
100 mA, Fixed Frequency
PWM Step-Up Micropower
Switching Regulator
The NCP1400A series are micropower stepup DC to DC
converters that are specifically designed for powering portable
equipment from one or two cell battery packs. These devices are
designed to startup with a cell voltage of 0.8 V and operate down to
less than 0.2 V. With only four external components, this series allows
a simple means to implement highly efficient converters that are
capable of up to 100 mA of output current.
Each device consists of an onchip fixed frequency oscillator, pulse
width modulation controller, phase compensated error amplifier that
ensures converter stability with discontinuous mode operation,
softstart, voltage reference, driver, and power MOSFET switch with
current limit protection. Additionally, a chip enable feature is provided
to power down the converter for extended battery life.
The NCP1400A device series are available in the Thin SOT235
package with six standard regulated output voltages. Additional
voltages that range from 1.8 V to 4.9 V in 100 mV steps can be
manufactured.
Features
Extremely Low StartUp Voltage of 0.8 V
Operation Down to Less than 0.2 V
Only Four External Components for Simple Highly Efficient
Converters
Up to 100 mA Output Current Capability
Fixed Frequency Pulse Width Modulation Operation
Phase Compensated Error Amplifier for Stable Converter Operation
Chip Enable Power Down Capability for Extended Battery Life
Typical Applications
Cellular Telephones
Pagers
Personal Digital Assistants
Electronic Games
Digital Cameras
Camcorders
Handheld Instruments
1
3
GND
CE
2
OUT
NC
4
LX
5
NCP1400A
V
out
V
in
Figure 1. Typical StepUp Converter Application
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THIN SOT235
SN SUFFIX
CASE 483
1
5
PIN CONNECTIONS AND
MARKING DIAGRAM
1
3
GND
CE
2
OUT
NC
4
LX
5
xxxYW
(Top View)
xxx = Marking
Y
= Year
W
= Work Week
See detailed ordering and shipping information in the ordering
information section on page 2 of this data sheet.
ORDERING INFORMATION
NCP1400A
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2
ORDERING INFORMATION
Device
Output
Voltage
Switching
Frequency
Marking
Package
Shipping
NCP1400ASN19T1
1.9 V
DAI
NCP1400ASN25T1
2.5 V
DAV
NCP1400ASN27T1
2.7 V
180 KHz
DAA
Thin SOT 23 5
3000 Units
NCP1400ASN30T1
3.0 V
180 KHz
DAB
Thin SOT235
3000 Units
on 7 Inch Reel
NCP1400ASN33T1
3.3 V
DAJ
NCP1400ASN50T1
5.0 V
DAD
NOTE: The ordering information lists six standard output voltage device options. Additional devices with output voltage ranging from 1.8 V
to 5.0 V in 100 mV increments can be manufactured. Contact your ON Semiconductor representative for availability.
ABSOLUTE MAXIMUM RATINGS
Rating
Symbol
Value
Unit
Power Supply Voltage (Pin 2)
V
OUT
0.3 to 6.0
V
Input/Output Pins
LX (Pin 5)
LX Peak Sink Current
V
LX
I
LX
0.3 to 6.0
400
V
mA
CE (Pin 1)
Input Voltage Range
Input Current Range
V
CE
I
CE
0.3 to 6.0
150 to 150
V
mA
Thermal Resistance Junction to Air
R
JA
250
C/W
Operating Ambient Temperature Range (Note 2)
T
A
40 to +85
C
Operating Junction Temperature Range
T
J
40 to +125
C
Storage Temperature Range
T
stg
55 to +150
C
NOTES:
1. This device series contains ESD protection and exceeds the following tests:
Human Body Model (HBM)
$
2.0 kV per JEDEC standard: JESD22A114.
Machine Model (MM)
$
200 V per JEDEC standard: JESD22A115.
2. The maximum package power dissipation limit must not be exceeded.
PD
+
TJ(max)
*
TA
R
q
JA
3. Latchup Current Maximum Rating:
$
150 mA per JEDEC standard: JESD78.
4. Moisture Sensitivity Level (MSL): 1 per IPC/JEDEC standard: JSTD020A.
NCP1400A
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3
ELECTRICAL CHARACTERISTICS
(For all values T
A
= 25
C, unless otherwise noted.)
Characteristic
Symbol
Min
Typ
Max
Unit
OSCILLATOR
Frequency (V
OUT
= V
SET
x 0.96, Note 5)
f
OSC
144
180
216
kHz
Frequency Temperature Coefficient (T
A
= 40
C to 85
C)
D
f
0.11
%/
C
Maximum PWM Duty Cycle (V
OUT
= V
SET
x 0.96)
D
MAX
68
75
82
%
Minimum Startup Voltage (I
O
= 0 mA)
V
start
0.8
0.95
V
Minimum Startup Voltage Temperature Coefficient (T
A
= 40
C to 85
C)
D
V
start
1.6
mV/
C
Minimum Operation Hold Voltage (I
O
= 0 mA)
V
hold
0.3
V
SoftStart Time (V
OUT
u
0.8 V)
t
SS
0.5
2.0
ms
LX (PIN 5)
LX Pin OnState Sink Current (V
LX
= 0.4 V)
Device Suffix:
19T1
25T1
27T1
30T1
33T1
50T1
I
LX
80
80
100
100
100
100
90
120
125
130
135
160
mA
Voltage Limit (V
OUT
= V
CE
= V
SET
x 0.96, V
LX
"L'' Side)
V
LXLIM
0.65
0.8
1.0
V
OffState Leakage Current (V
LX
= 5.0 V, T
A
= 40
C to 85
C)
I
LKG
0.5
1.0
A
CE (PIN 1)
CE Input Voltage (V
OUT
= V
SET
x 0.96)
High State, Device Enabled
Low State, Device Disabled
V
CE(high)
V
CE(low)
0.9
0.3
V
CE Input Current (Note 6)
High State, Device Enabled (V
OUT
= V
CE
= 5.0 V)
Low State, Device Disabled (V
OUT
= 5.0 V, V
CE
= 0 V)
I
CE(high)
I
CE(low)
0.5
0.5
0
0.15
0.5
0.5
A
TOTAL DEVICE
Output Voltage (V
in
u
0.8 V, I
O
= 4.0 mA)
Device Suffix:
19T1
25T1
27T1
30T1
33T1
50T1
V
OUT
1.853
2.438
2.633
2.925
3.218
4.875
1.9
2.5
2.7
3.0
3.3
5.0
1.948
2.563
2.768
3.075
3.383
5.125
V
Output Voltage Temperature Coefficient (T
A
= 40
C to +85
C)
Device Suffix:
19T1
25T1
27T1
30T1
33T1
50T1
D
V
OUT
100
100
100
100
100
150
ppm/
C
Operating Current 2 (V
OUT
= V
CE
= V
SET
+0.5 V, Note 5)
I
DD2
7.0
15
A
OffState Current (V
OUT
= 5.0 V, V
CE
= 0 V, T
A
= 40
C to +85
C, Note 6)
I
OFF
0.6
1.5
A
Operating Current 1 (V
OUT
= V
CE
= V
SET
x 0.96, f
OSC
= 180 kHz)
Device Suffix:
19T1
25T1
27T1
30T1
33T1
50T1
I
DD1
23
32
32
37
37
70
50
60
60
60
60
100
A
5. V
SET
means setting of output voltage.
6. CE pin is integrated with an internal 10 M
pullup resistor.
NCP1400A
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4
100
60
80
40
20
0
20
0
40
60
80
100
3.0
3.2
2.6
2.8
2.4
3.4
60
0
2.0
100
1.9
40
20
I
O
, OUTPUT CURRENT (mA)
V
OUT
, OUTPUT VOL
T
AGE (V)
1.8
I
O
, OUTPUT CURRENT (mA)
Figure 2. NCP1400ASN19T1 Output Voltage
vs. Output Current
Figure 3. NCP1400ASN30T1 Output Voltage
vs. Output Current
V
OUT
, OUTPUT VOL
T
AGE (V)
0
6.0
5.5
5.0
80
60
40
4.5
4.0
3.5
20
100
Figure 4. NCP1400ASN50T1 Output Voltage
vs. Output Current
I
O
, OUTPUT CURRENT (mA)
Figure 5. NCP1400ASN19T1 Efficiency vs.
Output Current
I
O
, OUTPUT CURRENT (mA)
EFFICIENCY (%)
V
OUT
, OUTPUT VOL
T
AGE (V)
Figure 6. NCP1400ASN30T1 Efficiency vs.
Output Current
I
O
, OUTPUT CURRENT (mA)
Figure 7. NCP1400ASN50T1 Efficiency vs.
Output Current
I
O
, OUTPUT CURRENT (mA)
EFFICIENCY (%)
EFFICIENCY (%)
2.1
0
60
40
20
80
100
0
80
60
40
20
100
0
80
60
40
100
20
20
80
40
0
100
0
80
60
40
20
100
V
in
= 1.5 V
1.7
1.6
60
80
V
in
= 0.9 V
V
in
= 1.2 V
V
in
= 1.5 V
V
in
= 0.9 V
V
in
= 1.2 V
V
in
= 2.0 V
V
in
= 1.5 V
V
in
= 0.9 V
V
in
= 1.2 V
V
in
= 1.5 V
V
in
= 0.9 V
V
in
= 2.0 V
V
in
= 3.0 V
V
in
= 1.2 V
V
in
= 0.9 V
V
in
= 2.0 V
V
in
= 2.5 V
V
in
= 1.5 V
V
in
= 3.0 V
V
in
= 0.9 V
V
in
= 2.0 V
V
in
= 1.5 V
NCP1400ASN19T1
L = 22
H
T
A
= 25
C
NCP1400ASN30T1
L = 22
H
T
A
= 25
C
NCP1400ASN50T1
L = 22
H
T
A
= 25
C
NCP1400ASN19T1
L = 22
H
T
A
= 25
C
NCP1400ASN50T1
L = 22
H
T
A
= 25
C
NCP1400ASN30T1
L = 22
H
T
A
= 25
C
NCP1400A
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5
1.0
0.8
0.6
0.4
0.2
0
100
80
60
40
20
0
100
80
60
40
20
0
1.0
0.8
0.6
0.4
0.2
0
1.0
0.8
0.6
0.4
0.2
0
1.5
80
70
3.5
60
50
4.0
3.0
2.5
4.5
V
OUT
, OUTPUT VOLTAGE (V)
I
DD1
, OPERA
TING CURRENT (
A)
40
30
20
10
0
2.0
T
A
, AMBIENT TEMPERATURE (
C)
Figure 8. NCP1400ASNXXT1 Operating
Current (I
DD1
) vs. Output Voltage
Figure 9. NCP1400ASN30T1 Current
Consumption vs. Temperature
I
DD1
, OPERA
TING CURRENT (
A)
Figure 10. NCP1400ASN50T1 Current
Consumption vs. Temperature
T
A
, AMBIENT TEMPERATURE (
C)
Figure 11. NCP1400ASN19T1 V
LX
Voltage Limit
vs. Temperature
T
A
, AMBIENT TEMPERATURE (
C)
V
LXLIM
, V
LX
, VOL
T
AGE LIMIT (V)
I
DD1
, OPERA
TING CURRENT (
A)
Figure 12. NCP1400ASN30T1 V
LX
Voltage Limit
vs. Temperature
T
A
, AMBIENT TEMPERATURE (
C)
Figure 13. NCP1400ASN50T1 V
LX
Voltage Limit
vs. Temperature
T
A
, AMBIENT TEMPERATURE (
C)
V
LXLIM
, V
LX
, VOL
T
AGE LIMIT (V)
V
LXLIM
, V
LX
, VOL
T
AGE LIMIT (V)
5.5
50
50
75
25
0
100
25
50
50
75
25
0
100
25
50
50
75
25
0
100
25
50
50
75
25
0
100
25
50
50
75
25
0
100
25
5.0
NCP1400ASNXXT1
L = 10
H
T
A
= 25
C
NCP1400ASN30T1
V
OUT
= 3.0 V x 0.96
Openloop Test
NCP1400ASN50T1
V
OUT
= 5.0 V x 0.96
Openloop Test
NCP1400ASN19T1
V
OUT
= 1.9 V x 0.96
NCP1400ASN30T1
V
OUT
= 3.0 V x 0.96
NCP1400ASN50T1
V
OUT
= 5.0 V x 0.96
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6
D
MAX
, MAXIMUM DUTY CYCLE (%)
4.8
4.7
4.6
4.9
5.0
5.1
80
70
60
90
100
200
150
100
50
0
250
300
2.9
2.8
2.7
3.0
3.1
3.2
T
A
, AMBIENT TEMPERATURE (
C)
V
OUT
, OUTPUT VOL
T
AGE (V)
T
A
, AMBIENT TEMPERATURE (
C)
Figure 14. NCP1400ASN30T1 Output Voltage
vs. Temperature
Figure 15. NCP1400ASN50T1 Output Voltage
vs. Temperature
V
OUT
, OUTPUT VOL
T
AGE (V)
Figure 16. NCP1400ASN30T1 Oscillator
Frequency vs. Temperature
T
A
, AMBIENT TEMPERATURE (
C)
Figure 17. NCP1400ASN50T1 Oscillator
Frequency vs. Temperature
T
A
, AMBIENT TEMPERATURE (
C)
f
OS
C
, OSCILLA
T
OR FREQUENCY (kHz)
f
OS
C
, OSCILLA
T
OR FREQUENCY (kHz)
Figure 18. NCP1400ASN30T1 Maximum Duty
Cycle vs. Temperature
T
A
, AMBIENT TEMPERATURE (
C)
Figure 19. NCP1400ASN50T1 Maximum Duty
Cycle vs. Temperature
T
A
, AMBIENT TEMPERATURE (
C)
50
50
75
25
0
100
25
50
50
75
25
0
100
25
50
50
75
25
0
100
25
50
50
100
25
0
25
200
150
100
50
0
250
300
50
50
75
25
0
100
25
50
40
75
80
70
60
90
100
50
50
100
25
0
25
50
40
75
NCP1400ASN30T1
V
OUT
= 3.0 V x 0.96
Openloop Test
NCP1400ASN30T1
L = 10
H
I
O
= 4.0 mA
V
in
= 1.2 V
NCP1400ASN50T1
L = 10
H
I
O
= 4.0 mA
V
in
= 1.2 V
NCP1400ASN50T1
V
OUT
= 5.0 V x 0.96
Openloop Test
NCP1400ASN50T1
V
OUT
= 5.0 V x 0.96
Openloop Test
NCP1400ASN30T1
V
OUT
= 3.0 V x 0.96
Openloop Test
D
MAX
, MAXIMUM DUTY CYCLE (%)
NCP1400A
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7
0.6
0.4
0.2
0.8
1.0
0.0
120
80
40
160
200
180
140
100
220
260
T
A
, AMBIENT TEMPERATURE (
C)
T
A
, AMBIENT TEMPERATURE (
C)
Figure 20. NCP1400ASN30T1 Startup/Hold
Voltage vs. Temperature
Figure 21. NCP1400ASN50T1 Startup/Hold
Voltage vs. Temperature
Figure 22. NCP1400ASN30T1 LX Pin OnState
Current vs. Temperature
T
A
, AMBIENT TEMPERATURE (
C)
Figure 23. NCP1400ASN50T1 LX Pin OnState
Current vs. Temperature
T
A
, AMBIENT TEMPERATURE (
C)
Figure 24. NCP1400ASNXXT1 LX Pin OnState
Current vs. Output Voltage
V
OUT
, OUTPUT VOLTAGE (V)
50
25
0
50
25
75
100
50
50
25
0
25
75
100
50
0
25
25
50
75
100
140
120
100
80
160
180
60
I
LX
, LX PIN ONST
A
TE CURRENT (mA)
V
star
t
, V
hold
, ST
AR
TUP AND HOLD VOL
T
AGE (V)
3.0
2.0
1.0
1.5
3.5
3.0
4.0
4.0
5.0
0
5.5
4.5
5.0
Figure 25. NCP1400ASNXXT1 LX Switch
OnResistance vs. Output Voltage
R
DS(on)
, LX SWITCH ONRESIST
ANCE (
)
0.6
0.4
0.2
0.8
1.0
0.0
50
25
0
50
25
75
100
2.5
2.0
1.5
3.5
3.0
4.0
5.5
4.5
5.0
2.5
2.0
NCP1400ASN30T1
L = 22
H
C
OUT
= 10
F
I
O
= 0 mA
NCP1400ASN50T1
V
LX
= 0.4 V
NCP1400ASN50T1
L = 22
H
C
OUT
= 10
F
I
O
= 0 mA
NCP1400ASN30T1
V
LX
= 0.4 V
NCP1400ASNXXT1
V
LX
= 0.4 V
T
A
= 25
C
NCP1400ASNXXT1
V
LX
= 0.4 V
T
A
= 25
C
V
OUT
, OUTPUT VOLTAGE (V)
V
star
t
, V
hold
, ST
AR
TUP AND HOLD VOL
T
AGE (V)
I
LX
, LX PIN ONST
A
TE CURRENT (mA)
I
LX
, LX PIN ONST
A
TE CURRENT (mA)
V
start
V
hold
V
start
V
hold
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8
0
20
25
15
10
5.0
30
80
60
40
20
0
1.6
0.6
0
1.6
1.4
1.2
1.0
0.8
0.6
0
80
60
40
20
0
80.0
60.0
40.0
20.0
0
1.6
1.4
1.2
1.0
I
O
, OUTPUT CURRENT (mA)
V
star
t
/V
hold
, ST
AR
TUP/HOLD VOL
T
AGE (V)
0.8
0.6
0.4
0.2
0
I
O
, OUTPUT CURRENT (mA)
Figure 26. NCP1400ASN19T1 Operation
Startup/Hold Voltage vs. Output Current
Figure 27. NCP1400ASN30T1 Operation
Startup/Hold Voltage vs. Output Current
Figure 28. NCP1400ASN50T1 Operation
Startup/Hold Voltage vs. Output Current
I
O
, OUTPUT CURRENT (mA)
Figure 29. NCP1400ASN19T1 Ripple Voltage
vs. Output Current
I
O
, OUTPUT CURRENT (mA)
V
ripple
, RIPPLE VOL
T
AGE (mV)
V
star
t
/V
hold
, ST
AR
TUP/HOLD VOL
T
AGE (V)
Figure 30. NCP1400ASN30T1 Ripple Voltage
vs. Output Current
I
O
, OUTPUT CURRENT (mA)
Figure 31. NCP1400ASN50T1 Ripple Voltage
vs. Output Current
I
O
, OUTPUT CURRENT (mA)
0
20
15
10
25
5.0
30
0
15
30
0
60
40
100
20
0
60
100
20
0
80
60
40
100
20
80
0.4
0.2
1.4
1.0
1.2
0.8
0.4
0.2
5.0
10
20
25
40
80
V
star
t
/V
hold
, ST
AR
TUP/HOLD VOL
T
AGE (V)
NCP1400ASN19T1
L = 22
H
C
OUT
= 68
F
T
A
= 25
C
NCP1400ASN30T1
L = 22
H
C
OUT
= 68
F
T
A
= 25
C
NCP1400ASN19T1
L = 22
H
C
OUT
= 68
F
T
A
= 25
C
NCP1400ASN50T1
L = 22
H
C
OUT
= 68
F
T
A
= 25
C
NCP1400ASN30T1
L = 22
H
C
OUT
= 68
F
T
A
= 25
C
NCP1400ASN50T1
L = 22
H
C
OUT
= 68
F
T
A
= 25
C
V
start
V
in
= 0.9 V
V
in
= 1.2 V
V
hold
V
start
V
hold
V
start
V
hold
V
in
= 1.5 V
V
in
= 0.9 V
V
in
= 3.0 V
V
in
= 1.5 V
V
in
= 2.0 V
V
in
= 0.9 V
V
in
= 1.5 V
V
in
= 1.5 V
V
in
= 2.0 V
V
ripple
, RIPPLE VOL
T
AGE (mV)
V
ripple
, RIPPLE VOL
T
AGE (mV)
NCP1400A
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9
V
OUT
= 3.0 V, V
in
= 1.2 V, I
O
= 10 mA., L = 22
m
H, C
OUT
= 68
m
F
1. V
LX
, 2.0 V/div
2. V
OUT
, 20 mV/div, AC coupled
3. I
L
, 100 mA/div
Figure 32. Operating Waveforms (Medium Load)
2
m
s/div
V
OUT
= 3.0 V, V
in
= 1.2 V, I
O
= 25 mA., L = 22
m
H, C
OUT
= 68
m
F
1. V
LX
, 2.0 V/div
2. V
OUT
, 20 mV/div, AC coupled
3. I
L
, 100 mA/div
Figure 33. Operating Waveforms (Heavy Load)
2
m
s/div
V
in
= 1.2 V, L = 22
m
H
1. V
OUT
=
1.9 V (AC coupled), 50 mV/div
2. I
O
= 3.0 mA to 30 mA
Figure 34. NCP1400ASN19T1
Load Transient Response
V
in
= 1.2 V, L = 22
m
H
1. V
OUT
=
1.9 V (AC coupled), 50 mV/div
2. I
O
= 30 mA to 3.0 mA
Figure 35. NCP1400ASN19T1
Load Transient Response
V
in
= 1.5 V, L = 22
m
H
1. V
OUT
=
3.0 V (AC coupled), 50 mV/div
2. I
O
= 3.0 mA to 30 mA
Figure 36. NCP1400ASN30T1
Load Transient Response
V
in
= 1.5 V, L = 22
m
H
1. V
OUT
= 3.0 V (AC coupled), 50 mV/div
2. I
O
= 30 mA to 3.0 mA
Figure 37. NCP1400ASN30T1
Load Transient Response
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V
in
= 1.5 V, L = 22
m
H
1. V
OUT
=
5.0 V (AC coupled), 50 mV/div
2. I
O
= 3.0 mA to 30 mA
Figure 38. NCP1400ASN50T1
Load Transient Response
V
in
= 1.5 V, L = 22
m
H
1. V
OUT
= 5.0 V (AC coupled), 50 mV/div
2. I
O
= 30 mA to 3.0 mA
Figure 39. NCP1400ASN50T1
Load Transient Response
-
+
VOLTAGE
REFERENCE
PHASE
COMPENSATION
SOFTSTART
PWM
CONTROLLER
180 kHz
OSCILLATOR
DRIVER
V
LX
LIMITER
LX
5
POWER
SWITCH
1 CE
GND
4
NC
3
OUT
2
ERROR
AMP
Figure 40. Representative Block Diagram
PIN FUNCTION DESCRIPTION
Pin #
Symbol
Pin Description
1
CE
Chip Enable Pin
(1) The chip is enabled if a voltage equal to or greater than 0.9 V is applied.
(2) The chip is disabled if a voltage less than 0.3 V is applied.
(3) The chip is enabled if this pin is left floating.
2
OUT
Output voltage monitor pin and also the power supply pin for the device.
3
NC
No internal connection to this pin.
4
GND
Ground pin.
5
LX
External inductor connection pin to power switch drain.
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DETAILED OPERATING DESCRIPTION
Operation
The NCP1400A series are monolithic power switching
regulators optimized for applications where power drain
must be minimized. These devices operate as fixed
frequency, voltage mode boost regulator and is designed to
operate in the discontinuous conduction mode. Potential
applications include low powered consumer products and
battery powered portable products.
The NCP1400A series are low noise fixed frequency
voltagemode PWM DCDC converters, and consist of
softstart circuit, feedback resistor, reference voltage,
oscillator, loop compensation network, PWM control
circuit, current limit circuit and power switch. Due to the
onchip feedback resistor and loop compensation network,
the system designer can get the regulated output voltage
from 1.8 V to 5.0 V with a small number of external
components. The quiescent current is typically 32
A
(V
OUT
= 2.7 V), and can be further reduced to about 1.5
A
when the chip is disabled (V
CE
t 0.3 V).
Soft Start
There is a soft start circuit in NCP1400A. When power is
applied to the device, the soft start circuit pumps up the
output voltage to approximately 1.5 V at a fixed duty cycle,
the level at which the converter can operate normally. What
is more, the startup capability with heavy loads is also
improved.
Oscillator
The oscillator frequency is internally set to 180 kHz at an
accuracy of
"20% and with low temperature coefficient of
0.11%/
C. Figures 16 and 17 illustrate oscillator frequency
versus temperature.
Regulated Converter Voltage (V
OUT
)
The V
OUT
is set by an internal feedback resistor network.
This is trimmed to a selected voltage from 1.8 V to 5.0 V
range in 100 mV steps with an accuracy of
"2.5%.
Compensation
The device is designed to operate in discontinuous
conduction mode. An internal compensation circuit was
designed to guarantee stability over the full input/output
voltage and full output load range. Stability cannot be
guaranteed in continuous conduction mode.
Current Limit
The NCP1400A series utilizes cyclebycycle current
limiting as a means of protecting the output switch
MOSFET from overstress and preventing the small value
inductor from saturation. Current limiting is implemented
by monitoring the output MOSFET current buildup during
conduction, and upon sensing an overcurrent conduction
immediately turning off the switch for the duration of the
oscillator cycle.
The voltage across the output MOSFET is monitored and
compared against a reference by the VLX limiter. When the
threshold is reached, a signal is sent to the PWM controller
block to terminate the output switch conduction. The current
limit threshold is typically set at 350 mA.
Enable/Disable Operation
The NCP1400A series offer IC shutdown mode by chip
enable pin (CE pin) to reduce current consumption. An
internal pullup resistor tied the CE pin to OUT pin by
default, i.e., user can float the pin CE for permanent "On''.
When voltage at pin CE is equal or greater than 0.9 V, the
chip will be enabled, which means the regulator is in normal
operation. When voltage at pin CE is less than 0.3 V, the chip
is disabled, which means IC is shutdown.
Important: DO NOT apply a voltage between 0.3 V to
0.9 V to pin CE as this voltage will place the IC into an
undefined state and the IC may drain excessive current
from the supply.
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APPLICATION CIRCUIT INFORMATION
Figure 41. Typical StepUp Converter Application
1
3
GND
CE
2
OUT
NC
4
LX
5
NCP1400A
V
out
V
in
C1
10
F
L1
D1
C2
68
F
22
H
Stepup Converter Design Equations
General stepup DCDC converter designed to operate in
discontinuous conduction mode can be defined by:
Calculation
Equation
D
t
on
T
I
PK
V
in
t
on
L
I
O
(V
in
)
2
(t
on
)
2
f
2L(V
out
)
V
F
*
V
in
)
NOTES:
D
Duty cycle
I
PK
Peak inductor current
I
O
Desired dc output current
V
in
Nominal operating dc input voltage
V
out
Desired dc output voltage
V
F
Diode forward voltage
Assume saturation voltage of the internal FET switch is negligible.
External Component Selection
Inductor
Inductance values between 18
H and 27
H are the best
suitable values for NCP1400A. In general, smaller
inductance values can provide larger peak inductor current
and output current capability, and lower conversion
efficiency, and vice versa. Select an inductor with smallest
possible DCR, usually less than 1.0
, to minimize loss. It
is necessary to choose an inductor with saturation current
greater than the peak current which the inductor will
encounter in the application.
Diode
The diode is the largest source of loss in DCDC
converters. The most importance parameters which affect
their efficiency are the forward voltage drop, V
F
, and the
reverse recovery time, trr. The forward voltage drop creates
a loss just by having a voltage across the device while a
current flowing through it. The reverse recovery time
generates a loss when the diode is reverse biased, and the
current appears to actually flow backwards through the
diode due to the minority carriers being swept from the PN
junction. A schottky diode with the following characteristics
is recommended:
Small forward voltage, V
F
t 0.3 V
Small reverse leakage current
Fast reverse recovery time/switching speed
Rated current larger than peak inductor current,
I
rated
u I
PK
Reverse voltage larger than output voltage,
V
reverse
u V
out
Input Capacitor
The input capacitor can stabilize the input voltage and
minimize peak current ripple from the source. The value of
the capacitor depends on the impedance of the input source
used. Small ESR (Equivalent Series Resistance) Tantalum
or ceramic capacitor with value of 10
F should be suitable.
Output Capacitor
The output capacitor is used for sustaining the output
voltage when the internal MOSFET is switched on and
smoothing the ripple voltage. Low ESR capacitor should be
used to reduce output ripple voltage. In general, a 47
F to
68
F low ESR (0.15
to
0.30
) Tantalum capacitor
should be appropriate.
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An evaluation board of NCP1400A has been made in the
small size of 23 mm x 20 mm and is shown in Figures 42 and
43. Please contact your ON Semiconductor representative
for availability. The evaluation board schematic diagram,
the artwork and the silkscreen of the surface mount PCB are
shown below:
20 mm
20 mm
23 mm
23 mm
Figure 42. NCP1400A PWM Stepup DCDC Converter Evaluation Board Silkscreen
Figure 43. NCP1400A PWM Stepup DCDC Converter Evaluation Board Artwork (Component Side)
1
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Components Supplier
Parts
Supplier
Part Number
Description
Phone
Inductor, L1
Sumida Electric Co. Ltd.
CD54220MC
Inductor 22
H/1.11 A
(852) 28806688
Schottky Diode, D1
ON Semiconductor Corp.
MBR0520LT1
Schottky Power Rectifier
(852) 26890088
Output Capacitor, C2
KEMET Electronics Corp.
T494D686K010AS
Low ESR Tantalum Capacitor
68
F/10 V
(852) 23051168
Input Capacitor, C1
KEMET Electronics Corp.
T491C106K016AS
Low Profile Tantalum Capacitor
10
F/16 V
(852) 23051168
PCB Layout Hints
Grounding
One point grounding should be used for the output power
return ground, the input power return ground, and the device
switch ground to reduce noise as shown in Figure 44, e.g.:
C2 GND, C1 GND, and U1 GND are connected at one point
in the evaluation board. The input ground and output ground
traces must be thick enough for current to flow through and
for reducing ground bounce.
Power Signal Traces
Low resistance conducting paths should be used for the
power carrying traces to reduce power loss so as to improve
efficiency (short and thick traces for connecting the inductor
L can also reduce stray inductance), e.g.: short and thick
traces listed below are used in the evaluation board:
1. Trace from TP1 to L1
2. Trace from L1 to Lx pin of U1
3. Trace from L1 to anode pin of D1
4. Trace from cathode pin of D1 to TP2
Output Capacitor
The output capacitor should be placed close to the output
terminals to obtain better smoothing effect on the output
ripple.
TP2
TP3
TP1
TP4
V
OUT
GND
V
in
GND
C1
10
F/16 V
L1
22
H
NCP1400A
U1
JP1
Enable
C2
68
F/10 V
On
Off
1
2
3
5
4
D1
MBR0520LT1
CE
OUT
NC
Gnd
LX
Figure 44. NCP1400A Evaluation Board Schematic Diagram
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PACKAGE DIMENSIONS
THIN SOT235
SN SUFFIX
CASE 48301
ISSUE B
NOTES:
1. DIMENSIONING AND TOLERANCING PER ANSI
Y14.5M, 1982.
2. CONTROLLING DIMENSION: MILLIMETER.
3. MAXIMUM LEAD THICKNESS INCLUDES LEAD
FINISH THICKNESS. MINIMUM LEAD THICKNESS
IS THE MINIMUM THICKNESS OF BASE
MATERIAL.
DIM
MIN
MAX
MIN
MAX
INCHES
MILLIMETERS
A
2.90
3.10 0.1142 0.1220
B
1.30
1.70 0.0512 0.0669
C
0.90
1.10 0.0354 0.0433
D
0.25
0.50 0.0098 0.0197
G
0.85
1.05 0.0335 0.0413
H
0.013
0.100 0.0005 0.0040
J
0.10
0.26 0.0040 0.0102
K
0.20
0.60 0.0079 0.0236
L
1.25
1.55 0.0493 0.0610
M
0
10
0
10
S
2.50
3.00 0.0985 0.1181
0.05 (0.002)
1
2
3
5
4
S
A
G
L
B
D
H
C
K
M
J
_
_
_
_
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ON Semiconductor and are trademarks of Semiconductor Components Industries, LLC (SCILLC). SCILLC reserves the right to make changes
without further notice to any products herein. SCILLC makes no warranty, representation or guarantee regarding the suitability of its products for any particular
purpose, nor does SCILLC assume any liability arising out of the application or use of any product or circuit, and specifically disclaims any and all liability,
including without limitation special, consequential or incidental damages. "Typical" parameters which may be provided in SCILLC data sheets and/or
specifications can and do vary in different applications and actual performance may vary over time. All operating parameters, including "Typicals" must be
validated for each customer application by customer's technical experts. SCILLC does not convey any license under its patent rights nor the rights of others.
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intended to support or sustain life, or for any other application in which the failure of the SCILLC product could create a situation where personal injury or
death may occur. Should Buyer purchase or use SCILLC products for any such unintended or unauthorized application, Buyer shall indemnify and hold
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attorney fees arising out of, directly or indirectly, any claim of personal injury or death associated with such unintended or unauthorized use, even if such claim
alleges that SCILLC was negligent regarding the design or manufacture of the part. SCILLC is an Equal Opportunity/Affirmative Action Employer.
PUBLICATION ORDERING INFORMATION
JAPAN: ON Semiconductor, Japan Customer Focus Center
4321 NishiGotanda, Shinagawaku, Tokyo, Japan 1410031
Phone: 81357402700
Email: r14525@onsemi.com
ON Semiconductor Website: http://onsemi.com
For additional information, please contact your local
Sales Representative.
NCP1400A/D
Literature Fulfillment:
Literature Distribution Center for ON Semiconductor
P.O. Box 5163, Denver, Colorado 80217 USA
Phone: 3036752175 or 8003443860 Toll Free USA/Canada
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