NJRC NJW4155GM1-A Current mode control internal 1.8a mosfet switching regulator ic for buck converter Datasheet

NJW4155
Current Mode Control
Internal 1.8A MOSFET Switching Regulator IC for Buck Converter
GENERAL DESCRIPTION
The NJW4155 is a buck converter with 40V/1.8A MOSFET. It
corresponds to high oscillating frequency, and Low ESR Output
Capacitor (MLCC) within wide input range from 4.5V to 40V.
Therefore, the NJW4155 can realize downsizing of applications
with a few external parts so that adopts current mode control.
Also, it has a soft start function, external clock synchronization,
over current protection and thermal shutdown circuit.
It is suitable for supplying power to a Car Accessory, Office
Automation Equipment, Industrial Instrument and so on.
■ PACKAGE OUTLINE
NJW4155GM1
NJW4155DL3
FEATURES
Current Mode Control
External Clock Synchronization
Wide Operating Voltage Range
4.5V to 40V
Switching Current
2.7A min.
PWM Control
Built-in Compensation Circuit
Correspond to Ceramic Capacitor (MLCC)
Oscillating Frequency
450kHz typ. (A, C ver.)
300kHz typ. (B ver.)
Soft Start Function
4ms typ.
UVLO (Under Voltage Lockout)
Over Current Protection (Hiccup type)
Thermal Shutdown Protection
Power Good Function (NJW4155GM1 only)
Standby Function
Package Outline
NJW4155GM1 : HSOP8
NJW4155DL3 : TO-252-5
Ver.2015-11-13
-1-
NJW4155
PRODUCT CLASSIFICATION
Version
Oscillation
Frequency
NJW4155GM1-A
A
450kHz typ.
HSOP8
NJW4155GM1-B
B
300kHz typ.
HSOP8
NJW4155DL3-B
B
300kHz typ.
TO-252-5
NJW4155GM1-C
C
450kHz typ.
HSOP8
(7pin: N.C.)
8
V+
SW
1
8
V+
+
Part Number
Power Good
Package
Operating Temperature
Range
General Spec.
Ta=-40 C to +125 C
General Spec.
Ta=-40 C to +125 C
General Spec.
Ta=-40 C to +125 C
General Spec.
Ta=-40 C to +125 C
PIN CONFIGURATION
SW
1
SW
2
7
V
SW
2
7
N.C.
GND
3
6
EN/SYNC GND
3
6
EN/SYNC
PG
4
5
IN-
4
5
IN-
Exposed PAD on
backside connect to GND
PG
5 EN/SYNC
4 IN3
3 GND
2 SW
1 V+
Exposed PAD on
backside connect to GND
NJW4155GM1-A
NJW4155GM1-B
NJW4155GM1-C
NJW4155DL3-B
PIN DESCRIPTIONS
PIN NUMBER
HSOP8 TO-252-5
GND
HSOP8
A ver.
B ver.
1
2
3
PG
4
4
–
IN-
5
5
4
EN/SYNC
6
6
5
N.C.
–
7
8
7
–
GND pin
Power Good pin. An open drain output that goes high impedance
when the IN- pin voltage is stable around 10%.(Only HSOP8 PKG)
Output Voltage Detecting pin
Connects output voltage through the resistor divider tap to this pin in
order to voltage of the IN- pin become 0.8V.
Standby Control pin
The EN/SYNC pin internally pulls down with 100k . Normal
Operation at the time of High Level. Standby Mode at the time of Low
Level or OPEN. Moreover, it operates by inputting clock signal at the
oscillatory frequency that synchronized with the input signal.
Non Connection
8
1
Power Supply pin for Power Line
–
–
–
Connect to GND (Only HSOP8 PKG)
PIN NAME
SW
+
V
Exposed
PAD
-2-
C ver.
1
2
3
FUNCTION
B ver.
2
Switch Output pin of Power MOSFET
3
Ver.2015-11-13
NJW4155
BLOCK DIAGRAM
V+
SLOPE
COMP.
CURRENT
SENSE
UVLO
OCP
EN/SYNC
High: ON
Low : OFF(Standby)
Enable
(Standby)
100k
SYNC
S Q
OSC
Buffer
R
PWM
SW
TSD
INER AMP
Soft Start
Vref
0.8V
PG
GND
Pow er Good
Control Logic
NJW4155GM1 only
Ver.2015-11-13
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NJW4155
ABSOLUTE MAXIMUM RATINGS
PARAMETER
SYMBOL
Supply Voltage
V+
V+- SW pin Voltage
VV-SW
EN/SYNC pin Voltage
VEN/SYNC
IN- pin Voltage
VINPower Good pin Voltage (*1)
VPG
Power Dissipation
Junction Temperature Range
Operating Temperature Range
Storage Temperature Range
PD
MAXIMUM RATINGS
-0.3~+45
+45
-0.3~+45
-0.3~+6
-0.3~+6
HSOP8
790 (*2)
2,500 (*3)
(Ta=25°C)
UNIT
V
V
V
V
V
mW
TO-252-5
Tj
Topr
Tstg
1,190 (*4)
3,125 (*3)
-40 to +150
-40 to +125
-50 to +150
C
C
C
(*1): Apply only the NJW4155GM1.
(*2): Mounted on glass epoxy board. (76.2×114.3×1.6mm:based on EIA/JDEC standard, 2Layers)
(*3): Mounted on glass epoxy board. (76.2×114.3×1.6mm:based on EIA/JDEC standard, 4Layers)
(For 4Layers: Applying 74.2×74.2mm inner Cu area and a thermal via hole to a board based on JEDEC standard JESD51-5)
2
(*4): Mounted on glass epoxy board. (76.2×114.3×1.6mm:based on EIA/JDEC standard size, 2Layers, Cu area 100mm )
RECOMMENDED OPERATING CONDITIONS
PARAMETER
SYMBOL
Supply Voltage
V+
Power Good pin Voltage (*5)
VPG
External Clock Input Range
A, C version
fSYNC
B version
(*5): Apply only the NJW4155GM1.
-4-
MIN.
4.5
0
TYP.
–
–
MAX.
40
5.5
UNIT
V
V
440
280
–
–
600
500
kHz
Ver.2015-11-13
NJW4155
(Unless otherwise noted, V+=VEN./SYNC=12V, Ta=25 C)
ELECTRICAL CHARACTERISTICS
PARAMETER
SYMBOL
Under Voltage Lockout Block
ON Threshold Voltage
OFF Threshold Voltage
Hysteresis Voltage
VT_ON
VT_OFF
VHYS
Soft Start Block
Soft Start Time
TEST CONDITION
MIN.
TYP.
MAX.
UNIT
V+= L → H
V+= H → L
4.2
4.1
70
4.4
4.3
90
4.5
4.4
–
V
V
mV
TSS
VB=0.75V
2
4
8
ms
fOSC
A, C version, VIN-=0.7V
B version, VIN-=0.7V
405
270
450
300
495
330
kHz
kHz
fDV
V+=4.5V to 40V
–
1
–
%
fDT
Ta=-40 C to +85 C
–
5
–
%
-1.0%
-0.1
0.8
–
+1.0%
+0.1
V
A
92
–
–
–
–
95.5
150
215
100
145
–
200
290
140
200
%
ns
ns
ns
ns
–
75
–
ms
–
2.7
–
0.2
3.4
–
0.4
4.0
3
A
A
Oscillator Block
Oscillation Frequency
Oscillation Frequency
deviation (Supply voltage)
Oscillation Frequency
deviation (Temperature)
Error Amplifier Block
Reference Voltage
Input Bias Current
PWM Comparate Block
Maximum Duty Cycle
Minimum ON Time1
(Use Built-in Oscillator)
Minimum ON Time2
(Use Ext CLK)
VB
IB
MAXDUTY
tON-min1
tON-min2
OCP Block
COOL DOWN Time
tCOOL
Output Block
Output ON Resistance
Switching Current Limit
SW Leak Current
RON
ILIM
ILEAK
Ver.2015-11-13
VIN-=0.7V
A, C version
B version
A, C version, fSYNC=500kHz
B version, fSYNC=400kHz
ISW=1.5A
VEN/SYNC=0V, V+=45V, VSW=0V
-5-
NJW4155
(Unless otherwise noted, V+=VEN/SYNC=12V, Ta=25 C)
ELECTRICAL CHARACTERISTICS
PARAMETER
Standby Control / Sync Block
EN/SYNC pin
High Threshold Voltage
EN/SYNC pin
Low Threshold Voltage
Input Bias Current
(EN/SYNC pin)
SYMBOL
VTHH_EN/SYNC
TEST CONDITION
VEN/SYNC= L → H
VTHL_EN/SYNC VEN/SYNC= H → L
Power Good Block (*6)
High Level Detection Voltage
Low Level Detection Voltage
Hysterisis Region
Power Good ON Resistance
Leak Current at OFF State
IEN
VTHH_PG
VTHL_PG
VHYS_PG
RON_PG
ILEAK_PG
VEN/SYNC=12V
Measured at IN- pin
Measured at IN- pin
IPG=10mA
VPG=6V
MIN.
TYP.
MAX.
UNIT
1.6
–
V+
V
0
–
0.5
V
–
170
250
A
105
85
–
–
–
110
90
2
37
–
115
95
–
50
0.1
A
–
3.5
4.2
mA
–
3.0
3.6
mA
–
–
3
A
General Characteristics
Quiescent Current
Standby Current
IDD
IDD_STB
A, C version,
RL=no load, VIN-=0.7V
B version,
RL=no load, VIN-=0.7V
VEN/SYNC=0V
(*6): Apply only the NJW4155GM1.
-6-
Ver.2015-11-13
NJW4155
THERMAL CHARACTERISTICS
PARAMETER
SYMBOL
Junction-to-ambient
thermal resistance
ja
Junction-to-Top of package
characterization parameter
jt
VALUE
158
HSOP8
50
105
TO-252-5
40
28
HSOP8
12
17
TO-252-5
12
UNIT
(*7)
(*8)
(*9)
(*8)
(*7)
(*8)
(*9)
(*8)
C/W
C/W
(*7): Mounted on glass epoxy board. (76.2×114.3×1.6mm:based on EIA/JDEC standard, 2Layers)
(*8): Mounted on glass epoxy board. (76.2×114.3×1.6mm:based on EIA/JDEC standard, 4Layers)
(For 4Layers: Applying 74.2×74.2mm inner Cu area and a thermal via hole to a board based on JEDEC standard JESD51-5)
2
(*9): Mounted on glass epoxy board. (76.2×114.3×1.6mm:based on EIA/JDEC standard size, 2Layers, Cu area 100mm )
POWER DISSIPATION vs. AMBIENT TEMPERATURE
NJW4155GM1 (HSOP8 Package)
Power Dissipation vs. Ambient Temperature
(Tj=~150°C)
NJW4155DL3 (TO-252-5 Package)
Power Dissipation vs. Ambient Temperature
(Tj=~150°C)
3500
At on 4 layer PC Board (*8)
At on 2 layer PC Board (*7)
2500
2000
1500
1000
500
0
Power Dissipation PD (mW)
Power Dissipation PD (mW)
3000
At on 4 layer PC Board (*8)
At on 2 layer PC Board (*9)
3000
2500
2000
1500
1000
500
0
-50
-25
0
25
50
75
100
Ambient Temperature Ta (°C)
Ver.2015-11-13
125
150
-50
-25
0
25
50
75
100
125
150
Ambient Temperature Ta (°C)
-7-
NJW4155
TYPICAL APPLICATIONS
V IN
CIN2
CIN1
L
EN/SYNC
EN/SYNC
High: ON
Low: OFF
(Standby)
Pow er Good
(NJW4155GM1 only)
V+
V OUT
SW
CFB
NJW4155
PG
IN-
R2
RFB
GND
SBD
COUT
R1
-8-
Ver.2015-11-13
NJW4155
TYPICAL CHARACTERISTICS (A, B, C version)
Reference Voltage vs. Supply Voltage
(Ta=25ºC)
0.81
Reference Voltage VB (V)
Reference Voltage VB (V)
0.81
0.805
0.8
0.795
0.805
0.8
0.795
0.79
0.79
0
10
20
30
Supply Voltage V+ (V)
40
-50
Switching Current Limit vs. Temperature
4.5
4
V+=12V
3.5
3
V+=40V
V+=5V
2.5
2
-25
0
25 50 75 100 125 150
Ambient Temperature Ta (ºC)
Output ON Resistance vs. Temperature
(ISW=1.5A)
0.4
Output ON Resistance RON (W)
Switching Current Limit ILIM (A)
5
Reference Voltage vs. Temperature
(V+=12V)
0.35
0.3
V+=5V
0.25
+
V+=12V V =40V
0.2
0.15
0.1
0.05
0
-50
Ver.2015-11-13
-25
0
25 50 75 100 125 150
Ambient Temperature Ta (ºC)
-50
-25
0
25 50 75 100 125 150
Ambient Temperature Ta (ºC)
-9-
NJW4155
TYPICAL CHARACTERISTICS (A, B, C version)
Under Voltage Lockout Voltage vs. Temperature
4.5
8
VT_ON
4.35
4.3
VT_OFF
4.25
4.2
Soft Start Time Tss (ms)
Threshold Voltage (V)
4.45
4.4
4.15
-50
5
4
3
-50
Switching Leak Current vs. Temperature
(V+=45V , VEN/SYNC=0V , VSW=0V)
9
8
7
6
5
4
3
2
1
-25
0
25 50 75 100 125 150
Ambient Temperature Ta (ºC)
Standby Current vs. Temperature
(VEN/SYNC=0V)
10
Standby Current IDD_STB (μA)
Switching Leak Current ILEAK (μA)
6
-25
0
25 50 75 100 125 150
Ambient Temperature Ta (ºC)
9
8
7
6
5
V+=40V
4
3
V+=12V
V+=4.5V
2
1
0
0
-50
- 10 -
7
2
4.1
10
Soft Start Time vs. Temperature
(V+=12V, VB=0.75V)
-25
0
25 50 75 100 125 150
Ambient Temperature Ta (ºC)
-50
-25
0
25 50 75 100 125 150
Ambient Temperature Ta (ºC)
Ver.2015-11-13
NJW4155
TYPICAL CHARACTERISTICS (A, C version)
Oscillation Frequency vs. Supply Voltage
(A, C ver., VIN-=0.7V, Ta=25ºC)
5
4.5
465
Quiescent Current IDD (mA)
Oscillation Frequnecny fOSC (kHz)
470
460
455
450
445
440
435
3.5
3
2.5
2
1.5
1
0
0
10
20
30
Supply Voltage V+ (V)
0
40
Oscillation Frequency vs Temperature
(A, C ver., V+=12V, VIN-=0.7V)
490
480
470
460
450
440
430
420
410
400
10
20
30
Supply Voltage V+ (V)
40
Maximum Duty Cycle vs. Temperature
(A, C ver., V+=12V, VIN-=0.7V)
100
Maximum Duty Cycle MAXDUTY (%)
500
Oscillation Frequency fosc (kHz)
4
0.5
430
99
98
97
96
95
94
93
92
91
90
-50
-25
0
25 50 75 100 125 150
Ambient Temperature Ta (ºC)
-50
Minimum ON Time1 vs. Temperature
(A, C ver., V+=12V)
200
190
-25
0
25 50 75 100 125 150
Ambient Temperature Ta (ºC)
Quiescent Current vs. Temperature
(A, C ver., RL=no load, VIN-=0.7V)
5
4.5
Quiescent Current IDD (mA)
Minimum ON Time1 tON-min1 (ns)
Quiescent Current vs. Supply Voltage
(A, C ver, RL=no load, VIN-=0.7V, Ta=25ºC)
180
170
160
150
140
130
120
110
4
3.5
3
2.5
V+=12V
V+=40V
V+=4.5V
2
1.5
1
0.5
100
0
-50
Ver.2015-11-13
-25
0
25 50 75 100 125 150
Ambient Temperature Ta (ºC)
-50
-25
0
25 50 75 100 125 150
Ambient Temperature Ta (ºC)
- 11 -
NJW4155
TYPICAL CHARACTERISTICS (B version)
Oscillation Frequency vs. Supply Voltage
(B ver., VIN-=0.7V, Ta=25ºC)
5
308
4.5
Quiescent Current IDD (mA)
Oscillation Frequnecny fOSC (kHz)
310
306
304
302
300
298
296
294
292
320
310
300
290
280
1.5
1
10
20
30
Supply Voltage V+ (V)
40
Maximum Duty Cycle vs. Temperature
(B ver., V+=12V, VIN-=0.7V)
100
99
98
97
96
95
94
93
92
91
-25
0
25 50 75 100 125 150
Ambient Temperature Ta (ºC)
-50
Minimum ON Time1 vs. Temperature
(B ver., V+=12V)
240
220
200
180
160
140
-25
0
25 50 75 100 125 150
Ambient Temperature Ta (ºC)
Quiescent Current vs. Temperature
(B ver., RL=no load, VIN-=0.7V)
4
Quiescent Current IDD (mA)
300
(ns)
2
90
-50
tON-min1
2.5
0
270
Minimum ON Time1
3
40
Maximum Duty Cycle MAXDUTY (%)
Oscillation Frequency fosc (kHz)
10
20
30
Supply Voltage V+ (V)
Oscillation Frequency vs Temperature
(B ver., V+=12V, VIN-=0.7V)
330
3.5
3
V+=4.5V
V+=40V
V+=12V
2.5
2
1.5
1
0.5
0
-50
- 12 -
3.5
0
0
260
4
0.5
290
280
Quiescent Current vs. Supply Voltage
(B ver, RL=no load, VIN-=0.7V, Ta=25ºC)
-25
0
25 50 75 100 125 150
Ambient Temperature Ta (ºC)
-50
-25
0
25 50 75 100 125 150
Ambient Temperature Ta (ºC)
Ver.2015-11-13
NJW4155 Application
Manual
NJW4155
Technical Information
Description of Block Features
1. Basic Functions / Features
Error Amplifier Section (ER AMP)
0.8V±1% precise reference voltage is connected to the non-inverted input of this section.
To set the output voltage, connects converter's output to inverted input of this section (IN- pin). If requires output
voltage over 0.8V, inserts resistor divider.
Because the optimized compensation circuit is built-in, the application circuit can be composed of minimum
external parts.
PWM Comparator Section (PWM), Oscillation Circuit Section (OSC)
The NJW4155 uses a constant frequency, current mode step down architecture. The oscillation frequency is
450kHz (typ.) at A, C version and 300kHz (typ.) at B version. The PWM signal is output by feedback of output
voltage and slope compensation switching current at the PWM comparator block.
The maximum duty ratio is 95.5% (typ.).
Table 1. Minimum ON time of NJW4155
A, C version
(fOSC =450kHz)
Use Built-in
150ns typ.
Oscillator
Use External
100ns typ.
Clock
(@ fSYNC=500kHz)
B version
(fOSC =300kHz)
215ns typ.
145ns typ.
(@ fSYNC=400kHz)
The buck converter of ON time is decided the following formula.
ton
VOUT
s
VIN fOSC
VIN shows input voltage and VOUT shows output voltage.
When the ON time becomes below in tON-min, in order to maintain output voltage at a stable state, change of duty or
pulse skip operation may be performed.
Power MOSFET (SW Output Section)
The power is stored in the inductor by the switch operation of built-in power MOSFET. The output current is limited
to 2.7A(min.) the overcurrent protection function. In case of step-down converter, the forward direction bias voltage is
generated with inductance current that flows into the external regenerative diode when MOSFET is turned off.
The SW pin allows voltage between the V+ pin and the SW pin up to +45V. However, you should use an Schottky
diode that has low saturation voltage.
Power Supply, GND pin (V+ and GND)
In line with switching element drive, current flows into the IC according to frequency. If the power supply
impedance provided to the power supply circuit is high, it will not be possible to take advantage of IC performance
due to input voltage fluctuation. Therefore insert a bypass capacitor close to the V+ pin – the GND pin connection in
order to lower high frequency impedance.
Ver.2015-11-13
- 13 -
NJW4155
NJW4155Application Manual
Technical Information
Description of Block Features (Continued)
2. Additional and Protection Functions / Features
Under Voltage Lockout (UVLO)
The UVLO circuit operating is released above V+=4.4V(typ.) and IC operation starts. When power supply voltage
is low, IC does not operate because the UVLO circuit operates. There is 90mV(typ.) width hysteresis voltage at rise
and decay of power supply voltage. Hysteresis prevents the malfunction at the time of UVLO operating and
releasing.
Soft Start Function (Soft Start)
The output voltage of the converter gradually rises to a set value by the soft start function. The soft start time is
4ms (typ.). It is defined with the time of the error amplifier reference voltage becoming from 0V to 0.75V. The soft
start circuit operates after the release UVLO and/or recovery from thermal shutdown.
0.8V
Vref,
IN- pin Voltage
OSC Waveform
ON
SW pin
OFF
UVLO(4.4V typ.) Release,
Standby,
Recover from Thermal
Shutdow n
Soft Start time: Tss=4ms(typ.) to V B=0.75V
Steady
Operaton
Soft Start effective period to V B=0.8V
Fig. 1. Startup Timing Chart
- 14 -
Ver.2015-11-13
NJW4155 Application
Manual
NJW4155
Technical Information
Description of Block Features (Continued)
Over Current Protection Circuit (OCP)
NJW4155 contains overcurrent protection circuit of hiccup architecture. The overcurrent protection circuit of hiccup
architecture is able to decrease heat generation at the overload.
The NJW4155 output returns automatically along with release from the over current condition.
At when the switching current becomes ILIM or more, the overcurrent protection circuit is stopped the MOSFET
output. The switching output holds low level down to next pulse output at OCP operating.
When the IN- pin voltage is 0.5V or lower(less), the switching operation stops after the overcurrent detection
continued 128 pulses.
After NJW4155 switching operation was stopped, it restarts by soft start function after the cool down time of approx
75ms (typ.).
IN- pin
Voltage
0.8V
0.5V
0V
Oscillation Frequency
A, C ver.=450kHz typ.
B ver.=300kHz typ.
ON
SW pin
OFF
Switching
Current
ILIM
0
Pulse Count : 128 pulse
Cool Down time :75ms typ.
Pulse by Pulse
Static Status
Detect Overcurrent
Soft Start
Fig. 2. Timing Chart at Over Current Detection
Thermal Shutdown Function (TSD)
When Junction temperature of the NJW4155 exceeds the 160°C*, internal thermal shutdown circuit function stops
SW function. When junction temperature decreases to 145°C* or less, SW operation returns with soft start operation.
The purpose of this function is to prevent malfunctioning of IC at the high junction temperature. Therefore it is not
something that urges positive use. You should make sure to operate within the junction temperature range rated
(150 C). (* Design value)
Standby Function
The NJW4155 stops the operating and becomes standby status when the EN/SYNC pin becomes less than 0.5V.
The EN/SYNC pin internally pulls down with 100k , therefore the NJW4155 becomes standby mode when the
EN/SYNC pin is OPEN. You should connect this pin to V+ when you do not use standby function.
Ver.2015-11-13
- 15 -
NJW4155
NJW4155Application Manual
Technical Information
Description of Block Features (Continued)
External Clock Synchronization
By inputting a square wave to EN/SYNC pin, can be synchronized to an external frequency.
You should fulfill the following specification about a square wave. (Table 2.)
Table 2. The input square wave to an EN/SYNC pin.
A, C version
B version
(fOSC =450kHz)
(fOSC =300kHz)
440kHz to
280kHz to
Input Frequency
600kHz
500kHz
Duty Cycle
25% to 75%
20% to 80%
Voltage
1.6V or more at High level
magnitude
0.5V or less at Low level
The trigger of the switching operating at the external synchronized mode is detected to the rising edge of the input
signal. At the time of switching operation from standby or asynchronous to synchronous operation, it has set a delay
time approx 20 s to 30 s in order to prevent malfunctions. (Fig. 3.)
High
EN/SYNC pin
Low
ON
SW pin
OFF
Standby
Delay Time
External Clock Synchronization
Fig. 3. Switching Operation by External Synchronized Clock
Power Good Function
It monitors the output status and outputs a signal from PG pin that internally connected to open drain MOSFET.
The Power Good pin goes high impedance when the IN- pin voltage is stable around 10%(typ.) of error amplifier
reference voltage.
A low on the pin indicates that the IN- pin voltage is out of the setting voltage.
To prevent malfunction of the Power Good output, it has hysterisis 2%(typ.) and the delay time approx 20 s to
30 s against the IN- pin voltage changes.
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Ver.2015-11-13
NJW4155 Application
Manual
NJW4155
Technical Information
Application Information
Inductors
Because a large current flows to the inductor, you should select the inductor with the large current capacity not to
saturate. Optimized inductor value is determined by the input voltage and output voltage.
The Inductor setting example is shown in Table 3.
Table 3. Inductor Setting Example
Input Voltage
VIN
Output Voltage
VOUT
3.3V
5.0V
8.0V
3.3V
5.0V
8.0V
12V
24V
Inductor L
A, C version
B version
(fOSC =450kHz)
(fOSC =300kHz)
27 H
39 H
33 H
47 H
33 H
47 H
39 H
47 H
47 H
56 H
47 H
56 H
When increasing inductor value, it is necessary to increasing capacity of an output capacitor and to secure the
stability of application. The minimum of inductor value is restricted from the following formula, when ON duty
exceeds 50%.
VIN 2 D ON 1
A, C version L
[ H]
1.11
VIN 2 D ON 1
B version
L
[ H]
0.74
Reducing L decreases the size of the inductor. However a peak current increases and adversely affects the
efficiency. (Fig. 4.)
Moreover, you should be aware that the output current is limited because it becomes easy to operating to the
overcurrent limit.
The peak current is decided the following formula.
IL
Ipk
VIN VOUT VOUT
[A]
L VIN fOSC
IL
[A]
2
IOUT
Current
Peak Current IPK
Indunctor
Ripple Current IL
Peak Current IPK
Output Current
IOUT
Indunctor
Ripple Current IL
0
tON
tOFF
Reducing L Value
tON
tOFF
Increasing L value
Fig. 4. Inductor Current State Transition (Continuous Conduction Mode)
Ver.2015-11-13
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NJW4155
NJW4155Application Manual
Technical Information
Application Information (Continued)
Input Capacitor
Transient current flows into the input section of a switching regulator responsive to frequency. If the power supply
impedance provided to the power supply circuit is large, it will not be possible to take advantage of the NJW4155
performance due to input voltage fluctuation. Therefore insert an input capacitor as close to the MOSFET as
possible. A ceramic capacitor is the optimal for input capacitor.
The effective input current can be expressed by the following formula.
IRMS
VOUT
IOUT
VIN
VOUT
VIN
[A]
In the above formula, the maximum current is obtained when VIN = 2 VOUT, and the result in this case is
IRMS = IOUT (MAX) 2.
When selecting the input capacitor, carry out an evaluation based on the application, and use a capacitor that has
adequate margin.
Output Capacitor
An output capacitor stores power from the inductor, and stabilizes voltage provided to the output.
Because NJW4155 corresponds to the output capacitor of low ESR, the ceramic capacitor is the optimal for
compensation. The output capacitor setting example is shown in Table 4.
Table 4. Output Capacitor Setting Example
Input Voltage
Output Voltage
VIN
VOUT
A, C version
3.3V
12V, 24V
5.0V
8.0V
B version
3.3V
12V, 24V
5.0V
8.0V
Capacitor
COUT
Part Number
47 F / 6.3V
22 F / 6.3V
22 F / 10V
GRM31CB30J476KE18: Murata
GRM31CB30J226ME18: Murata
GRM31CR61A226ME19: Murata
47 F / 6.3V +
22 F / 6.3V
47 F / 6.3V
47 F / 16V
GRM31CB30J476KE18: Murata
GRM31CB30J226ME18: Murata
GRM31CB30J476KE18: Murata
GRM32EB31C476KE15: Murata
The output capacitor uses capacity bigger than Table 4.
In addition, you should consider varied characteristics of capacitor (a frequency characteristic, a temperature
characteristic, a DC bias characteristic and so on) and unevenness peculiar to a capacitor supplier enough.
Therefore when selecting a capacitors, you should confirm the characteristics with supplier datasheets.
When selecting an output capacitor, you must consider Equivalent Series Resistance (ESR) characteristics, ripple
current, and breakdown voltage.
The output ripple noise can be expressed by the following formula.
Vripple(p
p)
ESR
IL [ V ]
The effective ripple current that flows in a capacitor (Irms) is obtained by the following equation.
Irms
- 18 -
IL
2 3
[ Arms]
Ver.2015-11-13
NJW4155 Application
Manual
NJW4155
Technical Information
Application Information (Continued)
Catch Diode
When the switch element is in OFF cycle, power stored in the inductor flows via the catch diode to the output
capacitor. Therefore during each cycle current flows to the diode in response to load current. Because diode's
forward saturation voltage and current accumulation cause power loss, a Schottky Barrier Diode (SBD), which has a
low forward saturation voltage, is ideal.
An SBD also has a short reverse recovery time. If the reverse recovery time is long, through current flows when
the switching transistor transitions from OFF cycle to ON cycle. This current may lower efficiency and affect such
factors as noise generation.
Setting Output Voltage, Compensation Capacitor
The output voltage VOUT is determined by the relative resistances of R1, R2. The current that flows in R1, R2 must
be a value that can ignore the bias current that flows in ER AMP.
R2
R1
VOUT
1
VB [ V ]
The zero points are formed with R2 and CFB, and it makes for the phase compensation of NJW4155.
The zero point is shown the following formula.
f Z1
2
1
[Hz]
R 2 C FB
You should set the zero point as a guide from 50kHz to 70kHz.
Output voltage setting resistor and compensation capacitor setting example is shown in Table 5.
Table 5. Output Voltage Setting Resistor and Compensation Capacitor Setting Example
Input Voltage
Output Voltage
R1
R2
CFB
VIN
VOUT
3.3V
180pF
4.7k
15k
12V, 24V
5.0V
150pF
3.0k
16k
8.0V
120pF
2.2k
20k
(A version, B version and C version are common.)
Ver.2015-11-13
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NJW4155
NJW4155Application Manual
Technical Information
Application Information (Continued)
Board Layout
In the switching regulator application, because the current flow corresponds to the oscillation frequency, the
substrate (PCB) layout becomes an important.
You should attempt the transition voltage decrease by making a current loop area minimize as much as possible.
Therefore, you should make a current flowing line thick and short as much as possible. Fig.5. shows a current loop
at step-down converter. Especially, should lay out high priority the loop of CIN-SW-SBD that occurs rapid current
change in the switching. It is effective in reducing noise spikes caused by parasitic inductance.
NJW4155
Built-in SW
VIN
CIN
NJW4155
Built-in SW
L
SBD
COUT
VIN
CIN
(a) Buck Converter SW ON
L
SBD
COUT
(b) Buck Converter SW OFF
Fig. 5. Current Loop at Buck Converter
Concerning the GND line, it is preferred to separate the power system and the signal system, and use single
ground point.
The voltage sensing feedback line should be as far away as possible from the inductance. Because this line has
high impedance, it is laid out to avoid the influence noise caused by flux leaked from the inductance.
Fig. 6. shows example of wiring at buck converter. Fig. 7 shows the PCB layout example.
L
V+
VIN
VOUT
SW
CIN
SBD
COUT
RL
(Bypass Capacitor)
NJW4155
CFB
INR2
GND
Separate Digital(Signal)
GND from Power GND
R1
To avoid the influence of the voltage drop,
the output voltage should be detected
near the load.
Because IN- pin is high impedance, the
voltage detection resistance: R1/R2 is put
as much as possible near IC(IN-).
Fig. 6. Board Layout at Buck Converter
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Ver.2015-11-13
NJW4155 Application
Manual
NJW4155
Technical Information
Application Information (Continued)
GND IN
VIN
SBD
CIN
EN/SYNC
L
Power
Good
COUT
R2
Power
GND Area
RFB
CFB
R1
COUT
VOUT
GNDOUT
Signal
GND Area
Feed back signal
HSOP8 Package (A version and B version)
Connect Signal GND line and Power GND line on backside pattern
Fig. 7. Layout Example (upper view)
Ver.2015-11-13
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NJW4155
NJW4155Application Manual
Technical Information
Calculation of Package Power
A lot of the power consumption of buck converter occurs from the internal switching element (Power MOSFET).
Power consumption of NJW4155 is roughly estimated as follows.
Input Power:
Output Power:
Diode Loss:
NJW4155 Power Consumption:
Where:
VIN
VOUT
VF
OFF duty
PIN = VIN IIN [W]
POUT = VOUT IOUT [W]
PDIODE = VF IL(avg) OFF duty [W]
PLOSS = PIN POUT PDIODE [W]
: Input Voltage for Converter
: Output Voltage of Converter
: Diode's Forward Saturation Voltage
: Switch OFF Duty
IIN
IOUT
IL(avg)
: Input Current for Converter
: Output Current of Converter
: Inductor Average Current
Efficiency ( ) is calculated as follows.
= (POUT PIN) 100 [%]
You should consider temperature derating to the calculated power consumption: PD.
You should design power consumption in rated range referring to the power dissipation vs. ambient temperature
characteristics.
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Ver.2015-11-13
NJW4155 Application
Manual
NJW4155
Technical Information
Application Design Examples
Buck Converter Application Circuit
IC
: NJW4155GM1
Input Voltage
: VIN=12V
Output Voltage
: VOUT=5V
Output Current
: IOUT=1.8A
Oscillation frequency : A, C version fosc=450kHz
: B version fosc=300kHz
VIN=12V
CIN2
Open
CIN1
10mF/50V
L
A ver. 15mH/3.2A
B ver. 22mH/2.7A
EN/SYNC
EN/SYNC
High: ON
Low: OFF
(Standby)
Power Good
V+
SW
CFB
150pF
NJW4155
PG
IN-
GND
(NJW4155GM1 only)
VOUT=-5V
SBD
COUT
47mF/16V
RFB
0W
(Short)
R2
16kW
R1
3kW
Reference
IC
Qty.
1
L
1
SBD
CIN1
CIN2
COUT
CFB
RFB
R1
R2
1
1
1
1
1
1
1
1
Ver.2015-11-13
Part Number
NJW4155GM1
A, C ver.: CLF10040T-150M
B ver.: CLF10040T-220M
CMS16
UMK325BJ106MM
Open
GRM32EB31C476KE15
150pF
0 (Short)
3k
16k
Description
Internal 1.8A MOSFET SW.REG. IC
Inductor 15 H, 3.2A
Inductor 22 H, 2.7A
Schottky Diode 40V, 3A
Ceramic Capacitor 3225 10 F, 50V, X5R
Optional
Ceramic Capacitor 3225 47 F, 16V, B
Ceramic Capacitor 1608 150pF, 50V, CH
Optional
Resistor 1608 3k , 1%, 0.1W
Resistor 1608 16k , 1%, 0.1W
Manufacturer
New JRC
TDK
TDK
Toshiba
Taiyo Yuden
Murata
Std.
Std.
Std.
- 23 -
NJW4155
NJW4155Application Manual
Technical Information
Application Characteristics
A, C version
Efficiency vs. Output Current
(VOUT=5V, Ta=25ºC)
100
6
f=450kHz
L=15 H
90
Efficiency
Output Voltage VOUT [V]
[%]
70
VIN=7V
VIN=12V
50
40
f=450kHz
L=15 H
5.8
80
60
Output Voltage vs. Output Current
(Ta=25ºC)
VIN=24V
30
20
10
5.6
5.4
5.2
VIN=7V, 12V, 24V
5
4.8
4.6
4.4
4.2
0
4
1
10
100
1000
Output Current IOUT [mA]
10000
1
10
100
1000
Output Current IOUT [mA]
10000
B version
Efficiency vs. Output Current
(VOUT=5V, Ta=25ºC)
100
6
f=300kHz
L=22 H
90
Efficiency
Output Voltage VOUT [V]
[%]
VIN=7V
VIN=12V
60
50
VIN=24V
40
30
20
10
5.6
5.4
5.2
VIN=7V, 12V, 24V
5
4.8
4.6
4.4
4.2
0
4
1
- 24 -
f=300kHz
L=22 H
5.8
80
70
Output Voltage vs. Output Current
(Ta=25ºC)
10
100
1000
Output Current IOUT [mA]
10000
1
10
100
1000
Output Current IOUT [mA]
10000
Ver.2015-11-13
NJW4155
MEMO
[CAUTION]
The specifications on this databook are only
given for information , without any guarantee
as regards either mistakes or omissions. The
application circuits in this databook are
described only to show representative usages
of the product and not intended for the
guarantee or permission of any right including
the industrial rights.
Ver.2015-11-13
- 25 -
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