MICROSEMI NX4108

NX4108
1A SYNCHRONOUS BUCK SWITCHER WITH FET ON BOARD
PRODUCTION DATA SHEET
Pb Free Product
DESCRIPTION
FEATURES
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The NX4108 is a current mode PWM buck switcher with
internal compensation, can provide up to 1A output current with FET on board. It operates from 2.8V to 5.5V
and output as low as 0.6V which is ideal for the application with single cell Li-Ion battery as well as other 3.3V
input bus supply applications. Switching frequency is
fixed 1MHz, small surface mount inductors and capaci- n
tors are allowed to use, make it good for portable appli- n
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cations.
NX4108 is available in 5-pin SOT23 package.
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SOT23-5L package
Internal Digital Soft Start
Internally-compensated Current Mode Controller
<1uA Shut-down Current
Peak Current Limit with HICCUP Feature and Over
Temperature Protection
Prebias Start-up Operation
Enable Available
Pb-free and RoHS Compliant
APPLICATIONS
Li-Ion Battery Operated Portable System
Cellular Phones
Portable Applications
USB Devices
TYPICAL APPLICATION
VIN=5V
1
FB
NX4108
5
EN
VIN
SW
GND
4
3
22uF(X5R,6.3V)
2.2uH
2
Vout=2.5V
10uF
(X5R,6.3V)
332k
105k
Figure1 - Typical application of NX4108CZ1TR
ORDERING INFORMATION
Device
NX4108CZ1TR
Rev. 1.7
12/30/09
Temperature
-40oC to 85oC
Package
SOT23-5L
Pb-Free
Yes
Microsemi
Analog Mixed Signal Group
11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570
1
NX4108
ABSOLUTE MAXIMUM RATINGS
VIN to GND ..................................................................... -0.3V to 6V
SW,FB,EN to GND ........................................................... -0.3V to VIN + 0.3V
ESD Susceptibility ............................................................. 1kV
Lead Temperature(Soldering,10sec.) .................................... 300oC
Storage Temperature Range ................................................ -55oC to 150oC
Operating Junction Temperature Range ................................ -40oC to 150oC
CAUTION: Stresses above those listed in "ABSOLUTE MAXIMUM RATINGS", may cause permanent damage to
the device. This is a stress only rating and operation of the device at these or any other conditions above those
indicated in the operational sections of this specification is not implied.
PACKAGE INFORMATION
5-LEAD PLASTIC SOT23
θJA ≈ 110o C/W
EN
1
GND
2
SW 3
5
FB
4
VIN
ELECTRICAL SPECIFICATIONS
VIN=3.5V. Typical data refers to TA= 25oC. Unless otherwise specified.
PARAMETER
Reference Voltage
Ref Voltage
Line Regualtion
Line Regulation
SYM
Test Condition
VFB
Min
TYP
MAX
Units
0.59
0.6
0.607
V
VIN=3V to 5V,VOUT=1.8V,
IOUT=10mA
VIN UVLO
VIN Rising Threshold
VIN Falling Threshold
Supply Voltage(VIN)
VIN Input Voltage Range
Shutdown Current
Quiescent Current
Oscillator (Rt)
Frequency
2
2.3
2.5
VIN
I shutdown
Iq
2.8
EN=GND
No Load, switching
FS
1
4
800
78
1000
5.5
2.5
1200
500
Microsemi
Analog Mixed Signal Group
11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570
V
uA
mA
kHz
%
nS
0.05
Tss
V
V
90
100
Error Amplifiers
Feedback Input Bias Current
SS
Rev. 1.7
12/30/09
2.8
2.3
Max Duty Cycle
Min ON time
Soft Start time
mV
uA
uS
2
NX4108
PARAMETER
Current Limit
Current Limit Threshold
Thermal Shutdown
Thermal shutdown trip point
Hysteresis
Internal Switch
Rdson of Control FET
Rdson of Synchronous FET
SYM
Test Condition
Min
TYP
MAX
Units
1.8
A
o
155
15
Vin=5V
Vin=3.3V
Vin=5V
Vin=3.3V
Enable
En low Threshold voltage
En high Threshold voltage
o
C
C
mohm
400
480
300
360
mohm
0.4
1.4
V
V
PIN DESCRIPTIONS
PIN SYMBOL
SW
GND
Ground Connection for Chip. Connect GND with large copper areas to the input and
output supply returns, and negative terminals of the input and output capacitors.
FB
Error amplifier inverting input. Error amplifier inverting input. This pin is connected via
resistor dividers to the output of the switching regulators to set the output DC voltage. A
332kohm resistor is recommended to be connected from VOUT and FB .
VIN
Supply voltage input for switcher.
EN
Rev. 1.7
12/30/09
PIN DESCRIPTION
SW output. Junction of the internal high-side and low-side power MOSFETs, and
output inductor.
Enable input. Set this pin to GND or less than 0.4V will shut down the regulator.
Enable signal can not be high when VIN is low.
Microsemi
Analog Mixed Signal Group
11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570
3
NX4108
BLOCK DIAGRAM
Thermal
Shutdown
UVLO
POR
EN
Vref
Bias
Generator
3 cycle
counter
POR
VIN
OCPB
+
-
CLK
VIN
Soft start
Hiccup
timer
OSC
70ns
one shot
reset dom
S
Q
R
+
start
Vref
PWM
FB
PWM comparator
1Mohm
OCPB
POR
20pF
Control
Logic
SW
VIN
LDen
GND
Figure 2 - Simplified block diagram of the NX4108
Rev. 1.7
12/30/09
Microsemi
Analog Mixed Signal Group
11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570
4
NX4108
Typical Operating Characteristics
R e ference voltage vs tem p e rature
0.604
0.603
Reference voltage(V)
0.602
0.601
0 .6
0.599
0.598
0.597
0.596
0.595
0.594
0.593
0
20
40
60
80
100
120
140
160
t e m p e r a t u r e (°C )
Fig.3 - Reference volateg vs temperature
Normalized frequency vs temperature
Normalized Frequency
1
0.98
0.96
0.94
0.92
0.9
0
20
40
60
80
100
120
140
160
temperature(°C)
Fig.4 - Normalized frequency vs temperature
Rev. 1.7
12/30/09
Microsemi
Analog Mixed Signal Group
11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570
5
NX4108
Typical Application( VOUT=2.5V)
VIN=5V
1
FB
NX4108
5
EN
VIN
SW
GND
4
3
22uF(X5R,6.3V)
2.2uH
Vout=2.5V
10uF
(X5R,6.3V)
2
332k
105k
Figure 5 - Demo board schematic
Figure 6 - Output ripple
Figure 7 - Transient response
Figure 8 - Efficiency
Rev. 1.7
12/30/09
Microsemi
Analog Mixed Signal Group
11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570
6
NX4108
Typical Application( VOUT=1.8V)
VIN=5V
1
FB
NX4108
5
EN
VIN
SW
GND
4
3
22uF(X5R,6.3V)
2.2uH
Vout=1.8V
10uF
(X5R,6.3V)
2
332k
165k
Figure 9 - Demo board schematic
Figure 10 - Output ripple
Figure 11 - Transient response
Figure12 - Efficiency
Rev. 1.7
12/30/09
Microsemi
Analog Mixed Signal Group
11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570
7
NX4108
Typical Application( VOUT=1.2V)
VIN=5V
1
FB
NX4108
5
EN
VIN
SW
GND
4
3
22uF(X5R,6.3V)
2.2uH
Vout=1.2V
10uF
(X5R,
6.3V)
2
332k
332k
Figure 13 - Demo board schematic
Figure 14 - Output ripple
Figure 15 - Transient response
Figure 17 - Shutdown
Figure 16 - Startup
Rev. 1.7
12/30/09
Microsemi
Analog Mixed Signal Group
11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570
8
NX4108
Typical Application( VOUT=1.2V)
Figure 18 - Efficiency
Rev. 1.7
12/30/09
Microsemi
Analog Mixed Signal Group
11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570
9
NX4108
Demoboard Layout
U1
VIN
1
VIN
4
C1
22u
VIN
SW
3
1
L1
VOUT
2
C2
10u
NX4108
FB
GND
332k
GND
EN
R1
5
R2
105k
2
1
VOUT
DO1608C-222
Figure 19 - Demoboard schematic
Figure 20- Top layer
Rev. 1.7
12/30/09
Microsemi
Analog Mixed Signal Group
11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570
10
NX4108
Figure 21- Gound layer
Figure 22- Power layer
Rev. 1.7
12/30/09
Microsemi
Analog Mixed Signal Group
11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570
11
NX4108
Figure 22- Bottom layer
Rev. 1.7
12/30/09
Microsemi
Analog Mixed Signal Group
11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570
12