NX7102
3A High Voltage Synchronous Buck Converter
P
RODUCTION
D
ATA
S
HEET
DESCRIPTION
KEY FEATURES
NX7102 is a 340kHz fixed
frequency, current mode, PWM
synchronous buck (step-down) DC-
DC converter, capable of driving a 3A
load with high efficiency, excellent
line and load regulation. The device
integrates N-channel power MOSFET
switches with low on-resistance.
Current mode control provides fast
transient response and cycle-by-cycle
current limit.
The controller is equipped with
output over-voltage protection which
protects the IC under an open load
condition. Additional safety features
include
under
voltage
lock-out
(UVLO), programmable soft-start and
over-temperature protection (OTP) to
protect the circuit.
This IC is available in SOIC-8 with
exposed pad package.
3A Synchronous Step-down
Regulator
Operational Input Supply
Voltage Range: 4. 5V-18V
Integrated Upper NMOS and
Lower NMOS
340kHz Switching Frequency
Input UVLO
Enable
Programmable External Soft-
Start
Cycle-By-Cycle Over-Current
Protection
Over Voltage Protection
Frequency Fold Back Under
Short Condition
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APPLICATIONS
Set-Top Box
LCD TV’s
Notebook/Netbook
PoE Powered Devices
PRODUCT HIGHLIGHT
12V
VIN
CIN
2x10uF(25V,X5R)
C4 0.1u
IN(2)
BST(1)
C5
10nF
L1
10uH
R1
26.1k
R2
10k
NX7102
SS(8)
SW(3)
EN(7)
FB(5)
GND(4) PAD COMP(6)
R3
10k
C3
5.6nF
3.3V
OUT
R4 100k
COUT
2*22uF(10V,X5R)
NX7102
Figure 1 –
12V Input, 3.3V Output with Ceramic Cap
PACKAGE ORDER INFO
T
A
(C)
-40 to 85
DE
Plastic SOIC 8 Pin
With Exposed Pad
RoHS Compliant / Pb-free
NX7102IDE
Note: Available in Tape & Reel. Append the letters “TR” to the part
number. (i.e. NX7102IDE-TR)
Copyright
2010
Rev.1.6, 2015-02-20
Microsemi
Analog Mixed Signal Group
One Enterprise, Aliso Viejo, CA, 949-380-6100, Fax: 949-215-4996
Page 1
NX7102
3A High Voltage Synchronous Buck Converter
P
RODUCTION
D
ATA
S
HEET
ABSOLUTE MAXIMUM RATINGS
Supply Input Voltage (VIN)............................................................................ -0.3V to 20V
Switch Voltage (SW) ............................................................................. -1V to (VIN + 1V)
EN ................................................................................................... -0.3V to (VIN + 0.3V)
BST ...................................................................................................-0.3V to (VSW + 6V)
COMP, FB, SS ................................................................................................. -0.3V to 6V
Maximum Operating Junction Temperature ............................................................... 150C
Storage Temperature Range .........................................................................-65C to 150C
Package Peak Temp. for Solder Reflow (40 seconds maximum exposure)................ 260°C
Note: Exceeding these ratings could cause damage to the device. All voltages are with respect to
Ground. Currents are positive into, negative out of specified terminal
.
PACKAGE PIN OUT
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BST 1
VIN
2
8 SS
7 EN
6 COMP
5 FB
MS C
7102I DE
XXXX
SW 3
GND
4
DE P
ACKAGE
(Top View)
DE P
ART
M
ARKING
“xxxx” Denote Date Code and Lot Identification
THERMAL DATA
RoHS / Pb-free 100% Matte Tin Pin Finish
DE
Plastic SOIC 8-Pin With Exposed Pad
60C/W
THERMAL RESISTANCE
-
JUNCTION TO
A
MBIENT
,
JA
Junction Temperature Calculation: T
J
= T
A
+ (P
D
x
JA
).
The
JA
numbers are guidelines for the thermal performance of the device/pc-board system. All of the
above assume no ambient airflow.
FUNCTIONAL PIN DESCRIPTION
Pin
1
2
3
4
5
Name
BST
VIN
SW
GND
FB
Description
Bootstrap pin. A minimum 10nF bootstrap capacitor is connected between the BS pin and SW pin.
The voltage across the bootstrap capacitor drives the internal high side NMOS.
Supply input pin. A capacitor should be connected between the VIN pin and GND pin to keep the
input voltage constant.
Power switch output pin. This pin is connected to the inductor and bootstrap capacitor.
Ground.
Feedback pin. This pin is connected to an external resistor divider to program the system output
voltage. When the FB pin voltage exceeds 20% of the nominal regulation value of 0.925V, the
over voltage protection is triggered. When the FB pin voltage is below 0.3V, the oscillator
frequency is lowered to realize short circuit protection.
Compensation pin. This pin is the output of the transconductance error amplifier and the input to
the current comparator. It is used to compensate the control loop. Connect a series RC network
from this pin to GND. In some cases, an additional capacitor from this pin to GND pin is required.
Control input pin. Forcing this pin above 2.7V enables the IC. Forcing this pin below 1.1V shuts
down the IC. When the IC is in shutdown mode, all functions are disabled to decrease the supply
current below 1μA.
Soft-start control input pin. SS controls the soft start period. Connect a capacitor from SS to GND
to set the soft-start period. A 0.1μF capacitor sets the soft-start period to 9ms. To disable the soft-
start feature, leave SS unconnected.
6
COMP
7
EN
NX7102
8
SS
Copyright
2010
Rev.1.6, 2015-02-20
Microsemi
Analog Mixed Signal Group
One Enterprise, Aliso Viejo, CA, 949-380-6100, Fax: 949-215-4996
Page 2
NX7102
3A High Voltage Synchronous Buck Converter
P
RODUCTION
D
ATA
S
HEET
RECOMMENDED OPERATING CONDITIONS
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Parameter
Input Operating Voltage
Maximum Output Current
Operating Ambient Temperature
Symbol
VIN
I
OUTMAX
T
A
Min
4. 5
3
-40
NX7102
Typ
Max
18
85
Units
V
A
°C
ELECTRICAL CHARACTERISTICS
Unless otherwise specified, the following specifications apply for V
IN
= V
EN
=12V, V
OUT
= 5V, T
A
= 25C.
NX7102
Parameter
Symbol
Test Conditions
Min
Typ
Max
½
Operating Current
Quiescent Current
I
Q
V
FB
= 1V
1.25
1.4
Shutdown Current
I
SHDN
V
EN
= 0V
.02
1
½
UVLO
V
IN
UVLO Threshold
V
UVLO
V
IN
Rising
3.65
4.00
4.25
Hysteresis
V
HYS
0.2
½
Feedback
Feedback Voltage
V
FB
T
A
= -40°C to 85°C
0.907 0.925 0.943
Feedback Bias Current
I
FB
V
FB
= 1V
-0.1
0.1
½
Oscillator
Internal Oscillator Frequency
F
OSC1
280
340
400
Short Circuit Oscillator
F
OSC2
100
Frequency
Maximum Duty Cycle
D
MAX
V
FB
= 0.8V
90
½
Minimum Duty Cycle
Error Amplifier
Error Amplifier
Transconductance
(1)
Voltage Gain
Current Sensing Gain
Current Sensing Gain
Soft-Start
Soft-start Current
Soft-start Time
Output Stage
High-side Switch On Resistance
Low-side Switch On Resistance
High-side Switch Leakage
Current
High-side Switch Current Limit
Low-side Switch Current Limit
½
EN
EN shutdown Threshold
EN shutdown Threshold
Hysteresis
V
ENH
V
ENL
1.1
1.5
350
2
D
MIN
G
EA
A
EA
G
CS
V
FB
= 1V
800
400
5.2
6
15
90
70
VIN = 18V, V
EN
= 0V, V
SW
= 0V
4.3
0.85
120
100
0.1
5.5
1.45
150
130
10
6.7
2.05
0
Units
mA
µA
V
V
V
µA
kHz
kHz
%
%
µA/V
V/V
A/V
µA
ms
mΩ
mΩ
µA
½
½
T
SS
R
DSONH
R
DSONL
I
LEAKH
I
LIMH
I
LIML
C
SS
= 0.1µF
½
NX7102
A
A
V
mV
Copyright
2010
Rev.1.6, 2015-02-20
Microsemi
Analog Mixed Signal Group
One Enterprise, Aliso Viejo, CA, 949-380-6100, Fax: 949-215-4996
Page 3
NX7102
3A High Voltage Synchronous Buck Converter
P
RODUCTION
D
ATA
S
HEET
ELECTRICAL CHARACTERISTICS (CONT)
Unless otherwise specified, the following specifications apply for V
IN
= V
EN
=12V, V
OUT
= 5V, T
A
= 25C.
NX7102
Parameter
Symbol
Test Conditions
Min
Typ
Max
EN Lockout Threshold
2.2
2.5
2.7
EN Lockout Hysteresis
210
½
Protection
Over Voltage Protection
V
FBOV
1.1
Threshold
FB Short Circuit Protection
0.23
0.3
0.41
Thermal Shutdown Threshold
T
OTSD
160
Thermal Shutdown Hysteresis
T
HYS
30
Notes:
1) Guaranteed by design, not tested.
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Units
mV
V
V
°C
°C
SIMPLIFIED BLOCK DIAGRAM
1.5V
EN
SD
0.925V
Bias
Regualtor
VIN
slope
Osc
340k/90k compensation
VCC Thermal
SD UVLOshutdown
Current
Sensing
BST
UVLO
PWM
LOGIC
SS
FB
COMP
2.5V
EN
1.3V
Low Side
Current Limit
0.3V
FB UVLO
GND
Soft Start
Driver
SW
NX7102
Figure 2 –
Simplified Block Diagram
Copyright
2010
Rev.1.6, 2015-02-20
Microsemi
Analog Mixed Signal Group
One Enterprise, Aliso Viejo, CA, 949-380-6100, Fax: 949-215-4996
Page 4
NX7102
3A High Voltage Synchronous Buck Converter
P
RODUCTION
D
ATA
S
HEET
APPLICATION CIRCUIT
W W W.
Microsemi
.COM
VIN
CIN
2x(10uF,25V)
C4 0.1u
IN(2)
BST(1)
NX7102
SS(8)
SW(3)
EN(7)
FB(5)
GND(4) PAD COMP(6)
C6
2200pF
C5
10nF
L1
22uH
R1
42.2k
R2
9.53k
OUT
COUT
1000uF,170mohm
R4 100k
Figure 3 –
12V Input, 5V Output with Electrolytic Cap
NX7102
Copyright
2010
Rev.1.6, 2015-02-20
Microsemi
Analog Mixed Signal Group
One Enterprise, Aliso Viejo, CA, 949-380-6100, Fax: 949-215-4996
Page 5
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