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PDF NX2141 Data sheet ( Hoja de datos )
| Número de pieza | NX2141 | |
| Descripción | SINGLE CHANNEL MOBILE PWM CONTROLLER | |
| Fabricantes | Microsemi | |
| Logotipo |  |
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NX2141
SINGLE CHANNEL MOBILE PWM CONTROLLER WITH
FEEDFORWARD AND ENABLE
ADVANCE DATA SHEET
Pb Free Product
DESCRIPTION
FEATURES
The NX2141 controller IC is a compact synchronous Buck n Bus voltage operation from 7V to 24V
controller IC designed for step down DC to DC con- n Less than 1uA shutdown current with Enable low
verter applications with voltage feedforward functionality. n Excellent dynamic response with input voltage feed-
Voltage feedforward provides fast response, good line forward and voltage mode control
regulation and nearly constant power stage gain under n Internal Digital Soft Start Function
wide voltage input range. The NX2141 controller is opti- n Fixed internal hiccup current limit
mized to convert single supply up to 24V bus voltage to n FB UVLO followed by hiccup feature
as low as 0.8V output voltage. Internal UVLO keeps the n Power Good indicator available
regulator off until the supply voltage exceeds 7V where n Start into precharged output
internal digital soft starts get initiated to ramp up output. n Pb-free and RoHS compliant
The NX2141 employs fixed current limiting and FB UVLO
followed by hiccup feature. Other features includes: 5V
gate drive capability , Adaptive dead band control, avail- n
able in 16 lead MLPQ and 10 lead MSOP package. n
n
APPLICATIONS
Notebook PC
Graphic Card on board converters
On board DC to DC such as
12V to 3.3V, 2.5V or 1.8V
n Set Top Box and LCD Display
TYPICAL APPLICATION
Vin1
1uH
+8 to 20V
100uF
MBR0530T1
1uF
25TQC33M
25V,33uF
Vin2
+5V
1uF 13 8 16
10
1uF
PVCC VIN
14 VCC
BST
Hdrv 1
0.1uF
M1
10k
ON
OFF
5 PGOOD
9 EN
SW 15
12 COMP
2.3k
1nF
15nF
11 FB
Pgnd
2
Ldrv 3
Gnd
17
1uH
M2 1.5k
2.2nF
Vout
+1.05V 10A
Co
2*2R5TPE220MC
(220uF,12mohm)
10k
32k
Figure1 - Typical application of NX2141(MLPQ)
ORDERING INFORMATION
Device
NX2141CMTR
NX2141CUTR
Temperature
-40o C to 85o C
-40o C to 85o C
Package
MLPQ-16L
MSOP-10L
Frequency
200kHz
200kHz
Pb-Free
Yes
Yes
Rev. 1.6
05/15/07
1
1 page  
BLOCK DIAGRAM
NX2141
FB
0.85Vref
/0.90Vref
VCC
Bias
Generator
VIN
6V/
5.5V
COMP
0.3V
START 0.8V
Digital
start Up
1.25V
0.8V
UVLO
VIN
OSC
ramp
POR
OC
SQ
R
FB
COMP
START
0.6V
CLAMP
1.3V
CLAMP
EN DISABLE
START
Control
Logic
PWM
DISABLE
OC
POR
Hiccup Logic
OCP
comparator
320mV
SS_half_done
70%*Vp
AGND
FB
PGOOD
BST
HDRV
SW
PVCC
LDRV
PGND
Figure 2 - Simplified block diagram of the NX2141(MLPQ)
Rev. 1.6
05/15/07
5
5 Page 
NX2141
APPLICATION INFORMATION
Current Ripple @ maximum input voltage is
calculated as
Symbol Used In Application Information:
VIN - Input voltage
VOUT
- Output voltage
IOUT - Output current
DVRIPPLE - Output voltage ripple
FS - Switching frequency
DIRIPPLE - Inductor current ripple
Design Example
Power stage design requirements:
VINMIN=8V
VINMAX=20V
VOUT=1.05V
IOUT_max =10A
DVRIPPLE <=30mV
DVTRAN<=50mV @ 5A step
FS=200kHz
Output Inductor Selection
The selection of inductor value is based on induc-
tor ripple current, power rating, working frequency and
efficiency. Larger inductor value normally means smaller
ripple current. However if the inductance is chosen too
large, it brings slow response and lower efficiency. Usu-
ally the ripple current ranges from 20% to 40% of the
output current. This is a design freedom which can be
decided by design engineer according to various appli-
cation requirements. The inductor value can be calcu-
lated by using the following equations:
LOUT
=
VINMAX -VOUT
IRIPPLE
× VOUT × 1
VINMAX FS
IRIPPLE=k ×IOUTPUT
where k is between 0.2 to 0.4.
Select k=0.4, then
...(1)
LOUT
=
20V-1.05V
0.4×10A
×
1.05V
20V
×
1
200kHz
LOUT =1.2uH
In this application we choose LOUT=1uH, then
coilcraft inductor MLC1550-102MLC is a good choice.
IRIPPLE
=
VIN -VOUT
LOUT
× VOUT
VIN
×1
FS
=20V-1.05V × 1.05V ×
1
...(2)
= 4.97A
1uH 20V 200kHz
Output Capacitor Selection
Output capacitor is basically decided by the
amount of the output voltage ripple allowed during steady
state(DC) load condition as well as specification for the
load transient. The optimum design may require a couple
of iterations to satisfy both condition.
Based on DC Load Condition
The amount of voltage ripple during the DC load
condition is determined by equation(3).
∆VRIPPLE
=
ESR × ∆IRIPPLE
+
∆IRIPPLE
8 × FS × COUT
...(3)
Where ESR is the output capacitors' equivalent
series resistance,COUT is the value of output capacitors.
Typically when large value capacitors are selected
such as Aluminum Electrolytic,POSCAP and OSCON
types are used, the amount of the output voltage ripple
is dominated by the first term in equation(3) and the
second term can be neglected.
For this example, POSCAP are chosen as output
capacitors, the ESR and inductor current typically de-
termines the output voltage ripple.
ESRdesire
=
∆VRIPPLE
∆IRIPPLE
=
30mV
4.97A
= 6mΩ
...(4)
If low ESR is required, for most applications, mul-
tiple capacitors in parallel are better than a big capaci-
tor. For example, for 30mV output ripple, POSCAP
2R5TPE220MC with 12mΩ are chosen.
N = E S R E × ∆ IR I P P L E
∆ VRIPPLE
Number of Capacitor is calculated as
...(5)
N = 12mΩ× 4.97A
30mV
N =2
The number of capacitor has to be round up to a
integer. Choose N =2.
Rev. 1.6
05/15/07
11
11 Page | ||
| Páginas | Total 21 Páginas | |
| PDF Descargar | [ Datasheet NX2141.PDF ] | |
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