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NX4108
1A SYNCHRONOUS BUCK SWITCHER WITH FET ON BOARD
PRODUCTION DATA SHEET Pb Free Product
DESCRIPTION
FEATURES
n n n n n 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
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 n cations. NX4108 is available in 5-pin SOT23 package. n n n n
APPLICATIONS
Li-Ion Battery Operated Portable System Cellular Phones Portable Applications USB Devices
TYPICAL APPLICATION
VIN=5V 1 5 EN FB VIN SW GND 4 3 2
22uF(X5R,6.3V)
Figure1 - Typical application of NX4108CZ1TR
NX4108
2.2uH
Vout=2.5V
10uF (X5R,6.3V)
332k
105k
ORDERING INFORMATION
Device NX4108CZ1TR Temperature -40oC to 85oC Package SOT23-5L Pb-Free Yes
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
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
JA 110o C/W
EN GND
1 2
5
FB
SW 3
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 VIN UVLO VIN Rising Threshold VIN Falling Threshold Supply Voltage(VIN) VIN Input Voltage Range Shutdown Current Quiescent Current Oscillator (Rt) Frequency Max Duty Cycle Min ON time Error Amplifiers Feedback Input Bias Current SS Soft Start time
Rev. 1.7 12/30/09
SYM VFB
Test Condition
Min 0.59
TYP 0.6 2
MAX 0.607
Units V mV
VIN=3V to 5V,VOUT=1.8V, IOUT=10mA 2.3
2.5 2.3
2.8
V V
VIN I shutdown Iq FS EN=GND No Load, switching
2.8 1 4 800 78 1000 90 100
5.5 2.5
V uA mA kHz % nS
1200
0.05 Tss 500
uA uS
Microsemi
Analog Mixed Signal Group 11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570
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 Enable En low Threshold voltage En high Threshold voltage SYM Test Condition Min TYP 1.8 155 15 Vin=5V Vin=3.3V Vin=5V Vin=3.3V 400 480 300 360 0.4 1.4 MAX Units A
o o
C C
mohm mohm
V V
PIN DESCRIPTIONS
PIN SYMBOL SW PIN DESCRIPTION SW output. Junction of the internal high-side and low-side power MOSFETs, and output inductor. 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. 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 . Supply voltage input for switcher. 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.
GND
FB
VIN EN
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
3
NX4108
BLOCK DIAGRAM
Thermal Shutdown POR EN POR VIN CLK VIN start Soft start Hiccup timer OSC 70ns one shot reset dom S Q R
+
UVLO
Vref
Bias Generator
3 cycle counter OCPB
+ -
Vref PWM FB 1Mohm 20pF PWM comparator OCPB POR VIN LDen Control Logic SW
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 0.602 Reference voltage(V) 0.601 0 .6 0.599 0.598 0.597 0.596 0.595 0.594 0.593 0 20 40 60 80 t e m p e r a t u r e (C ) 100 120 140 160
Fig.3 - Reference volateg vs temperature
Normalized frequency vs temperature 1 Normalized Frequency 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 5 EN FB VIN SW GND 4 3 2
22uF(X5R,6.3V)
Figure 5 - Demo board schematic
NX4108
2.2uH
Vout=2.5V
10uF (X5R,6.3V)
332k
105k
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 5 EN FB VIN SW GND 4 3 2
22uF(X5R,6.3V)
Figure 9 - Demo board schematic
NX4108
2.2uH
Vout=1.8V
10uF (X5R,6.3V)
332k
165k
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 5 EN FB VIN SW GND 4 3 2
22uF(X5R,6.3V)
Figure 13 - Demo board schematic
NX4108
2.2uH 10uF (X5R, 6.3V)
Vout=1.2V
332k
332k
Figure 14 - Output ripple
Figure 15 - Transient response
Figure 16 - Startup
Rev. 1.7 12/30/09
Figure 17 - Shutdown
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 2 VOUT VOUT
DO1608C-222 C2 10u 5 R1 332k R2 105k GND
NX4108
FB EN GND 2 1
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

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