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NCP1400A 100 mA, Fixed Frequency PWM Step-Up Micropower Switching Regulator
The NCP1400A series are micropower step-up DC to DC converters that are specifically designed for powering portable equipment from one or two cell battery packs. These devices are designed to start-up 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 on-chip fixed frequency oscillator, pulse width modulation controller, phase compensated error amplifier that ensures converter stability with discontinuous mode operation, soft-start, 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 SOT-23-5 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.
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5 1 THIN SOT-23-5 SN SUFFIX CASE 483
PIN CONNECTIONS AND MARKING DIAGRAM
CE OUT NC 1 xxxYW 2 3 5 LX
* Extremely Low Start-Up 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 Cellular Telephones Pagers Personal Digital Assistants Electronic Games Digital Cameras Camcorders Handheld Instruments
4
GND
xxx = Marking Y = Year W = Work Week (Top View)
ORDERING INFORMATION
See detailed ordering and shipping information in the ordering information section on page 2 of this data sheet.
Typical Applications
Vin CE 1 OUT 2 NC 3 NCP1400A LX 5
Vout
GND 4
Figure 1. Typical Step-Up Converter Application
(c) Semiconductor Components Industries, LLC, 2002
1
January, 2002 - Rev. 4
Publication Order Number: NCP1400A/D
NCP1400A
ORDERING INFORMATION
Device NCP1400ASN19T1 NCP1400ASN25T1 NCP1400ASN27T1 NCP1400ASN30T1 NCP1400ASN33T1 NCP1400ASN50T1 Output Voltage 1.9 V 2.5 V 2.7 V 3.0 V 3.3 V 5.0 V 180 KHz Switching Frequency Marking DAI DAV DAA DAB DAJ DAD Thin SOT 23 5 SOT-23-5 3000 Units on 7 Inch Reel Package Shipping
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
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Power Supply Voltage (Pin 2) Input/Output Pins LX (Pin 5) LX Peak Sink Current CE (Pin 1) Input Voltage Range Input Current Range VOUT VLX ILX -0.3 to 6.0 -0.3 to 6.0 400 V V mA V mA VCE ICE -0.3 to 6.0 -150 to 150 250 Thermal Resistance Junction to Air RJA TA TJ C/W C C C Operating Ambient Temperature Range (Note 2) Operating Junction Temperature Range Storage Temperature Range -40 to +85 -40 to +125 -55 to +150 Tstg NOTES: 1. This device series contains ESD protection and exceeds the following tests: Human Body Model (HBM) $2.0 kV per JEDEC standard: JESD22-A114. Machine Model (MM) $200 V per JEDEC standard: JESD22-A115. 2. The maximum package power dissipation limit must not be exceeded. TJ(max) * TA PD + RqJA 3. Latch-up Current Maximum Rating: $150 mA per JEDEC standard: JESD78. 4. Moisture Sensitivity Level (MSL): 1 per IPC/JEDEC standard: J-STD-020A.
Rating
Symbol
Value
Unit
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NCP1400A
ELECTRICAL CHARACTERISTICS (For all values TA = 25C, unless otherwise noted.)
Characteristic OSCILLATOR Frequency (VOUT = VSET x 0.96, Note 5) Frequency Temperature Coefficient (TA = -40C to 85C) Maximum PWM Duty Cycle (VOUT = VSET x 0.96) Minimum Start-up Voltage (IO = 0 mA) Minimum Start-up Voltage Temperature Coefficient (TA = -40C to 85C) Minimum Operation Hold Voltage (IO = 0 mA) Soft-Start Time (VOUT u 0.8 V) LX (PIN 5) LX Pin On-State Sink Current (VLX = 0.4 V) Device Suffix: 19T1 25T1 27T1 30T1 33T1 50T1 Voltage Limit (VOUT = VCE = VSET x 0.96, VLX "L'' Side) Off-State Leakage Current (VLX = 5.0 V, TA = -40C to 85C) CE (PIN 1) CE Input Voltage (VOUT = VSET x 0.96) High State, Device Enabled Low State, Device Disabled CE Input Current (Note 6) High State, Device Enabled (VOUT = VCE = 5.0 V) Low State, Device Disabled (VOUT = 5.0 V, VCE = 0 V) TOTAL DEVICE Output Voltage (Vin u 0.8 V, IO = 4.0 mA) Device Suffix: 19T1 25T1 27T1 30T1 33T1 50T1 Output Voltage Temperature Coefficient (TA = -40C to +85C) Device Suffix: 19T1 25T1 27T1 30T1 33T1 50T1 Operating Current 2 (VOUT = VCE = VSET +0.5 V, Note 5) Off-State Current (VOUT = 5.0 V, VCE = 0 V, TA = -40C to +85C, Note 6) Operating Current 1 (VOUT = VCE = VSET x 0.96, fOSC = 180 kHz) Device Suffix: 19T1 25T1 27T1 30T1 33T1 50T1 5. VSET means setting of output voltage. 6. CE pin is integrated with an internal 10 M pull-up resistor. VOUT 1.853 2.438 2.633 2.925 3.218 4.875 DVOUT - - - - - - IDD2 IOFF IDD1 - - - - - - 23 32 32 37 37 70 50 60 60 60 60 100 - - 100 100 100 100 100 150 7.0 0.6 - - - - - - 15 1.5 A A A 1.9 2.5 2.7 3.0 3.3 5.0 1.948 2.563 2.768 3.075 3.383 5.125 ppm/C V V VCE(high) VCE(low) ICE(high) ICE(low) 0.9 - -0.5 -0.5 - - 0 0.15 - 0.3 A 0.5 0.5 ILX 80 80 100 100 100 100 VLXLIM ILKG 0.65 - 90 120 125 130 135 160 0.8 0.5 - - - - - - 1.0 1.0 V A mA fOSC Df DMAX Vstart DVstart Vhold tSS 144 - 68 - - 0.3 0.5 180 0.11 75 0.8 -1.6 - 2.0 216 - 82 0.95 - - - kHz %/C % V mV/C V ms Symbol Min Typ Max Unit
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NCP1400A
2.1 VOUT, OUTPUT VOLTAGE (V) VOUT, OUTPUT VOLTAGE (V)
3.4
2.0 Vin= 1.5 V 1.9 Vin= 0.9 V 1.8 NCP1400ASN19T1 L = 22 H TA = 25C 0 20 40 60 80 100 Vin= 1.2 V
3.2 Vin= 2.0 V 3.0 Vin= 0.9 V 2.8 NCP1400ASN30T1 L = 22 H TA = 25C 0 20 40 60 80 100 Vin= 1.2 V Vin= 1.5 V
1.7
2.6
1.6
2.4 IO, OUTPUT CURRENT (mA) IO, OUTPUT CURRENT (mA)
Figure 2. NCP1400ASN19T1 Output Voltage vs. Output Current
6.0 VOUT, OUTPUT VOLTAGE (V) 100
Figure 3. NCP1400ASN30T1 Output Voltage vs. Output Current
5.5 Vin= 3.0 V 5.0 Vin= 0.9 V 4.5 NCP1400ASN50T1 L = 22 H TA = 25C 0 20 40 60 80 100 Vin= 1.5 V Vin= 2.0 V EFFICIENCY (%)
80 Vin= 1.5 V 60 Vin= 0.9 V 40 NCP1400ASN19T1 L = 22 H TA = 25C 0 20 40 60 80 100 Vin= 1.2 V
4.0
20
3.5
0 IO, OUTPUT CURRENT (mA)
IO, OUTPUT CURRENT (mA)
Figure 4. NCP1400ASN50T1 Output Voltage vs. Output Current
100 Vin= 2.5 V EFFICIENCY (%) EFFICIENCY (%) 80 Vin= 2.0 V 60 Vin= 0.9 V Vin= 1.2 V Vin= 1.5 V 80 100
Figure 5. NCP1400ASN19T1 Efficiency vs. Output Current
Vin= 3.0 V Vin= 0.9 V Vin= 1.5 V Vin= 2.0 V
60
40 NCP1400ASN30T1 L = 22 H TA = 25C 0 20 40 60 80 100
40 NCP1400ASN50T1 L = 22 H TA = 25C 0 20 40 60 80 100
20
20 0
0 IO, OUTPUT CURRENT (mA)
IO, OUTPUT CURRENT (mA)
Figure 6. NCP1400ASN30T1 Efficiency vs. Output Current
Figure 7. NCP1400ASN50T1 Efficiency vs. Output Current
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NCP1400A
80 IDD1, OPERATING CURRENT (A) 70 60 50 40 30 20 10 0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 NCP1400ASNXXT1 L = 10 H TA = 25C IDD1, OPERATING CURRENT (A)
100
80
60
40 NCP1400ASN30T1 VOUT = 3.0 V x 0.96 Open-loop Test -25 0 25 50 75 100
20
0 -50
VOUT, OUTPUT VOLTAGE (V)
TA, AMBIENT TEMPERATURE (C)
Figure 8. NCP1400ASNXXT1 Operating Current (IDD1) vs. Output Voltage
100 IDD1, OPERATING CURRENT (A) VLXLIM, VLX, VOLTAGE LIMIT (V) 1.0
Figure 9. NCP1400ASN30T1 Current Consumption vs. Temperature
80
0.8
60
0.6
40 NCP1400ASN50T1 VOUT = 5.0 V x 0.96 Open-loop Test -25 0 25 50 75 100
0.4
20
0.2 NCP1400ASN19T1 VOUT = 1.9 V x 0.96 0 -50 -25 0 25 50 75 100
0 -50
TA, AMBIENT TEMPERATURE (C)
TA, AMBIENT TEMPERATURE (C)
Figure 10. NCP1400ASN50T1 Current Consumption vs. Temperature
1.0 VLXLIM, VLX, VOLTAGE LIMIT (V) VLXLIM, VLX, VOLTAGE LIMIT (V) 1.0
Figure 11. NCP1400ASN19T1 VLX Voltage Limit vs. Temperature
0.8
0.8
0.6
0.6
0.4 NCP1400ASN30T1 VOUT = 3.0 V x 0.96
0.4 NCP1400ASN50T1 VOUT = 5.0 V x 0.96
0.2
0.2
0 -50
-25
0
25
50
75
100
0 -50
-25
0
25
50
75
100
TA, AMBIENT TEMPERATURE (C)
TA, AMBIENT TEMPERATURE (C)
Figure 12. NCP1400ASN30T1 VLX Voltage Limit vs. Temperature
Figure 13. NCP1400ASN50T1 VLX Voltage Limit vs. Temperature
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NCP1400A
3.2 VOUT, OUTPUT VOLTAGE (V) VOUT, OUTPUT VOLTAGE (V)
5.1
3.1
5.0
3.0
4.9
2.9 NCP1400ASN30T1 L = 10 H IO = 4.0 mA Vin = 1.2 V -25 0 25 50 75 100
4.8 NCP1400ASN50T1 L = 10 H IO = 4.0 mA Vin = 1.2 V -25 0 25 50 75 100
2.8
4.7
2.7 -50
4.6 -50
TA, AMBIENT TEMPERATURE (C)
TA, AMBIENT TEMPERATURE (C)
Figure 14. NCP1400ASN30T1 Output Voltage vs. Temperature
fOSC, OSCILLATOR FREQUENCY (kHz) fOSC, OSCILLATOR FREQUENCY (kHz) 300 250 200 150 100 50 0 -50 NCP1400ASN30T1 VOUT = 3.0 V x 0.96 Open-loop Test -25 0 25 50 75 100 300 250 200 150 100 50 0 -50
Figure 15. NCP1400ASN50T1 Output Voltage vs. Temperature
NCP1400ASN50T1 VOUT = 5.0 V x 0.96 Open-loop Test -25 0 25 50 75 100
TA, AMBIENT TEMPERATURE (C)
TA, AMBIENT TEMPERATURE (C)
Figure 16. NCP1400ASN30T1 Oscillator Frequency vs. Temperature
100 DMAX, MAXIMUM DUTY CYCLE (%) DMAX, MAXIMUM DUTY CYCLE (%) 90 80 70 60 50 40 -50 NCP1400ASN30T1 VOUT = 3.0 V x 0.96 Open-loop Test -25 0 25 50 75 100 100 90 80 70 60 50 40 -50
Figure 17. NCP1400ASN50T1 Oscillator Frequency vs. Temperature
NCP1400ASN50T1 VOUT = 5.0 V x 0.96 Open-loop Test -25 0 25 50 75 100
TA, AMBIENT TEMPERATURE (C)
TA, AMBIENT TEMPERATURE (C)
Figure 18. NCP1400ASN30T1 Maximum Duty Cycle vs. Temperature
Figure 19. NCP1400ASN50T1 Maximum Duty Cycle vs. Temperature
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NCP1400A
Vstart, Vhold, STARTUP AND HOLD VOLTAGE (V) Vstart, Vhold, STARTUP AND HOLD VOLTAGE (V)
1.0 Vstart 0.8
1.0 Vstart
0.8 NCP1400ASN50T1 L = 22 H COUT = 10 F IO = 0 mA
0.6
0.4
NCP1400ASN30T1 L = 22 H COUT = 10 F IO = 0 mA
0.6
0.4
Vhold 0.2
0.2
Vhold
0.0 -50
-25
0
25
50
75
100
0.0 -50
-25
0
25
50
75
100
TA, AMBIENT TEMPERATURE (C)
TA, AMBIENT TEMPERATURE (C)
Figure 20. NCP1400ASN30T1 Startup/Hold Voltage vs. Temperature
ILX, LX PIN ON-STATE CURRENT (mA) ILX, LX PIN ON-STATE CURRENT (mA) 200 260
Figure 21. NCP1400ASN50T1 Startup/Hold Voltage vs. Temperature
160
220
120
180
80 NCP1400ASN30T1 VLX = 0.4 V 40 -50 -25 0 25 50 75 100
140 NCP1400ASN50T1 VLX = 0.4 V 100 -50 -25 0 25 50 75 100
TA, AMBIENT TEMPERATURE (C)
TA, AMBIENT TEMPERATURE (C)
Figure 22. NCP1400ASN30T1 LX Pin On-State Current vs. Temperature
ILX, LX PIN ON-STATE CURRENT (mA) 180 160 140 120 100 80 60 1.5 NCP1400ASNXXT1 VLX = 0.4 V TA = 25C RDS(on), LX SWITCH ON-RESISTANCE () 5.0
Figure 23. NCP1400ASN50T1 LX Pin On-State Current vs. Temperature
4.0
3.0
2.0 NCP1400ASNXXT1 VLX = 0.4 V TA = 25C 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5
1.0 0 1.5
2.0
2.5
3.0
3.5
4.0
4.5
5.0
5.5
VOUT, OUTPUT VOLTAGE (V)
VOUT, OUTPUT VOLTAGE (V)
Figure 24. NCP1400ASNXXT1 LX Pin On-State Current vs. Output Voltage
Figure 25. NCP1400ASNXXT1 LX Switch On-Resistance vs. Output Voltage
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NCP1400A
Vstart/Vhold, STARTUP/HOLD VOLTAGE (V) Vstart/Vhold, STARTUP/HOLD VOLTAGE (V)
1.6 1.4 1.2 1.0 0.8 0.6 0.4 0.2 0 0 5.0 10 15 20 25 30 IO, OUTPUT CURRENT (mA) Vhold NCP1400ASN19T1 L = 22 H COUT = 68 F TA = 25C Vstart
1.6 1.4 1.2 1.0 0.8 0.6 0.4 0.2 0 0 5.0 10 15 NCP1400ASN30T1 L = 22 H COUT = 68 F TA = 25C 20 25 30 Vstart
Vhold
IO, OUTPUT CURRENT (mA)
Figure 26. NCP1400ASN19T1 Operation Startup/Hold Voltage vs. Output Current
Vstart/Vhold, STARTUP/HOLD VOLTAGE (V) 1.6 1.4 Vstart 1.2 1.0 0.8 0.6 0.4 0.2 0 0 5.0 10 15 NCP1400ASN50T1 L = 22 H COUT = 68 F TA = 25C 20 25 30 Vhold Vripple, RIPPLE VOLTAGE (mV) 80.0
Figure 27. NCP1400ASN30T1 Operation Startup/Hold Voltage vs. Output Current
NCP1400ASN19T1 L = 22 H COUT = 68 F TA = 25C
60.0
40.0 Vin= 1.2 V Vin= 1.5 V 20.0 Vin= 0.9 V
0
0
20
40
60
80
100
IO, OUTPUT CURRENT (mA)
IO, OUTPUT CURRENT (mA)
Figure 28. NCP1400ASN50T1 Operation Startup/Hold Voltage vs. Output Current
80 Vripple, RIPPLE VOLTAGE (mV) Vripple, RIPPLE VOLTAGE (mV) Vin= 2.0 V 60 Vin= 1.5 V 80
Figure 29. NCP1400ASN19T1 Ripple Voltage vs. Output Current
60
NCP1400ASN50T1 L = 22 H COUT = 68 F TA = 25C Vin= 0.9 V
Vin= 2.0 V
40
Vin= 1.5 V NCP1400ASN30T1 L = 22 H COUT = 68 F TA = 25C 40 60 80 100
40 Vin= 1.5 V 20 Vin= 3.0 V
Vin= 0.9 V 20
0
0
20
0
0
20
40
60
80
100
IO, OUTPUT CURRENT (mA)
IO, OUTPUT CURRENT (mA)
Figure 30. NCP1400ASN30T1 Ripple Voltage vs. Output Current
Figure 31. NCP1400ASN50T1 Ripple Voltage vs. Output Current
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NCP1400A
2 ms/div VOUT = 3.0 V, Vin = 1.2 V, IO = 10 mA., L = 22 mH, COUT = 68 mF 1. VLX, 2.0 V/div 2. VOUT, 20 mV/div, AC coupled 3. IL, 100 mA/div
2 ms/div VOUT = 3.0 V, Vin = 1.2 V, IO = 25 mA., L = 22 mH, COUT = 68 mF 1. VLX, 2.0 V/div 2. VOUT, 20 mV/div, AC coupled 3. IL, 100 mA/div
Figure 32. Operating Waveforms (Medium Load)
Figure 33. Operating Waveforms (Heavy Load)
Vin = 1.2 V, L = 22 mH 1. VOUT = 1.9 V (AC coupled), 50 mV/div 2. IO = 3.0 mA to 30 mA
Vin = 1.2 V, L = 22 mH 1. VOUT = 1.9 V (AC coupled), 50 mV/div 2. IO = 30 mA to 3.0 mA
Figure 34. NCP1400ASN19T1 Load Transient Response
Figure 35. NCP1400ASN19T1 Load Transient Response
Vin = 1.5 V, L = 22 mH 1. VOUT = 3.0 V (AC coupled), 50 mV/div 2. IO = 3.0 mA to 30 mA
Vin = 1.5 V, L = 22 mH 1. VOUT = 3.0 V (AC coupled), 50 mV/div 2. IO = 30 mA to 3.0 mA
Figure 36. NCP1400ASN30T1 Load Transient Response http://onsemi.com
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Figure 37. NCP1400ASN30T1 Load Transient Response
NCP1400A
Vin = 1.5 V, L = 22 mH 1. VOUT = 5.0 V (AC coupled), 50 mV/div 2. IO = 3.0 mA to 30 mA
Vin = 1.5 V, L = 22 mH 1. VOUT = 5.0 V (AC coupled), 50 mV/div 2. IO = 30 mA to 3.0 mA
Figure 38. NCP1400ASN50T1 Load Transient Response
Figure 39. NCP1400ASN50T1 Load Transient Response
OUT 2 ERROR AMP
VLX LIMITER
LX 5
+ NC 3
DRIVER
POWER SWITCH
PHASE COMPENSATION
PWM CONTROLLER
VOLTAGE REFERENCE GND 4
SOFT-START
180 kHz OSCILLATOR
1 CE
Figure 40. Representative Block Diagram
PIN FUNCTION DESCRIPTION
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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. Output voltage monitor pin and also the power supply pin for the device. No internal connection to this pin. Ground pin. 2 3 4 5 OUT NC GND LX External inductor connection pin to power switch drain.
Pin #
Symbol
Pin Description
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NCP1400A
DETAILED OPERATING DESCRIPTION
Operation Compensation
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 voltage-mode PWM DC-DC converters, and consist of soft-start circuit, feedback resistor, reference voltage, oscillator, loop compensation network, PWM control circuit, current limit circuit and power switch. Due to the on-chip 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 (VOUT = 2.7 V), and can be further reduced to about 1.5 A when the chip is disabled (VCE t 0.3 V).
Soft Start
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 cycle-by-cycle 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 build-up 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
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 start-up 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 (VOUT)
The VOUT 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%.
The NCP1400A series offer IC shutdown mode by chip enable pin (CE pin) to reduce current consumption. An internal pull-up 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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NCP1400A
APPLICATION CIRCUIT INFORMATION
L1 Vin C1 10 F CE 1 OUT 2 NC 3 22 H NCP1400A
D1 Vout LX 5 C2 68 F
GND 4
Figure 41. Typical Step-Up Converter Application
Step-up Converter Design Equations
Diode
General step-up DC-DC converter designed to operate in discontinuous conduction mode can be defined by:
Calculation D Equation t on T
IPK IO
V int on L
(V in) 2(t on) 2f 2L(V out ) V F * V in)
NOTES: D - Duty cycle IPK - Peak inductor current IO - Desired dc output current Vin - Nominal operating dc input voltage Vout - Desired dc output voltage VF - Diode forward voltage Assume saturation voltage of the internal FET switch is negligible.
External Component Selection
Inductor
The diode is the largest source of loss in DC-DC converters. The most importance parameters which affect their efficiency are the forward voltage drop, VF , 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 P-N junction. A schottky diode with the following characteristics is recommended: Small forward voltage, VF t 0.3 V Small reverse leakage current Fast reverse recovery time/switching speed Rated current larger than peak inductor current, Irated u IPK Reverse voltage larger than output voltage, Vreverse u Vout
Input Capacitor
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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.
12
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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NCP1400A
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
1
23 mm
Figure 42. NCP1400A PWM Step-up DC-DC Converter Evaluation Board Silkscreen
20 mm
23 mm
Figure 43. NCP1400A PWM Step-up DC-DC Converter Evaluation Board Artwork (Component Side)
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NCP1400A
Components Supplier
Parts Inductor, L1 Supplier Sumida Electric Co. Ltd. Part Number CD54-220MC Description Inductor 22 H/1.11 A Phone (852) 2880-6688 (852) 2689-0088 (852) 2305-1168 (852) 2305-1168
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Schottky Diode, D1 ON Semiconductor Corp.AAAAAA Schottky Power Rectifier MBR0520LT1 KEMET Electronics Corp. KEMET Electronics Corp. T494D686K010AS T491C106K016AS Output Capacitor, C2 Input Capacitor, C1 Low ESR Tantalum Capacitor 68 F/10 V Low Profile Tantalum Capacitor 10 F/16 V
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
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
Low resistance conducting paths should be used for the power carrying traces to reduce power loss so as to improve
The output capacitor should be placed close to the output terminals to obtain better smoothing effect on the output ripple.
TP2 VOUT C2 68 F/10 V TP3 GND JP1 Enable On Off
D1 MBR0520LT1
L1 22 H C1 10 F/16 V
TP1 Vin
CE 1 OUT 2 NC 3 NCP1400A U1
LX 5
TP4 GND
Gnd 4
Figure 44. NCP1400A Evaluation Board Schematic Diagram
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NCP1400A
PACKAGE DIMENSIONS
THIN SOT-23-5 SN SUFFIX CASE 483-01 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 A B C D G H J K L M S MILLIMETERS MIN MAX 2.90 3.10 1.30 1.70 0.90 1.10 0.25 0.50 0.85 1.05 0.013 0.100 0.10 0.26 0.20 0.60 1.25 1.55 0_ 10 _ 2.50 3.00 INCHES MIN MAX 0.1142 0.1220 0.0512 0.0669 0.0354 0.0433 0.0098 0.0197 0.0335 0.0413 0.0005 0.0040 0.0040 0.0102 0.0079 0.0236 0.0493 0.0610 0_ 10 _ 0.0985 0.1181
D
5 1 2 4 3
S
B
L G A J C 0.05 (0.002) H K M
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NCP1400A
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PUBLICATION ORDERING INFORMATION
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NCP1400A/D

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