NCP3120
Dual 2.0 A, Step-Down
DC/DC Switching Regulator
The NCP3120 is a dual buck converter designed for low voltage
applications requiring high efficiency. This device is capable of
producing an output voltage as low as 0.8 V. The NCP3120 provides
dual 2.0 A switching regulators with an adjustable 200 kHz
−
750 kHz
switching frequency. The switching frequency is set by an external
resistor. The NCP3120 also incorporates an auto−tracking and
sequencing feature. Protection features include cycle−by−cycle
current limit and undervoltage lockout (UVLO). The NCP3120 comes
in a 32−pin QFN package.
Features
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MARKING DIAGRAM
1
1
32
NCP3120
AWLYYWWG
G
•
•
•
•
•
•
•
•
•
•
•
Input Voltage Range from 4.5 V to 13.2 V
12 V
in
to 5.0 V
out
= 87% Efficiency Min @ 2.0 A
200−750 kHz Operation
Stable with Low ESR Ceramic Output Capacitor
0.8
±1.5%
FB Reference Voltage
External Soft−Start
Out of Phase Operation of OUT1 & OUT2
Auto−Tracking and Sequencing
Enable/Disable Capability
Hiccup Overload Protection
Low Shutdown Power (I
q
< 100
mA)
QFN32
CASE 488AM
NCP3120 = Specific Device Code
A
= Assembly Location
WL
= Wafer Lot
YY
= Year
WW
= Work Week
G
= Pb−Free Package
(Note: Microdot may be in either location)
ORDERING INFORMATION
See detailed ordering and shipping information in the package
dimensions section on page 40 of this data sheet.
Typical Applications
•
Set−Top Boxes, Portable Applications, Networking and
Telecommunications
•
DSP/mP/FPGA Core
VIN
RVIN
FB1
R_TRACK
PG1
Enable
Disable
Enable
Disable
EN2
PG2
EN1
R14
R24
C3
AVIN
GND
PG1
PG2
EN1
SEQ1
EN2
SEQ2
COMP2
COMP1
AGND
AGND
TRACK1,2
FB2
RT
SW2
SS1
OUT1
SW1
L11
D11
GND
VIN
C1
GND
L21
D21
C12
C22
R23
R13
C13
GND
GND
R22
GND
GND
C2
GND
R12
GND
OUT2
GND
R11
C11
NCP3120
GND
SS2
R21
C21
RT
GND
C23
GND
GND
Figure 1. Typical Application Circuit
©
Semiconductor Components Industries, LLC, 2010
October, 2010
−
Rev. 2
1
Publication Order Number:
NCP3120/D
NCP3120
0 .1. ref
Falling comp
SHDN 1
PG 1
0 .9 . ref
pg 1
HS protection 1
Delay
VIN
COMP 1
Error Amplifier
FB 1
EOTA 1
PWM
0o
R
CON TR OL
LOGIC 1
S
HS1
SW 1
1V
10 u
SS 1
TRACK 1
Soft Start &
Tracking Control
(MUX1)
10 u
OSCILLATOR
RT
SEQ1
EN 1
Power
Sequencing 1
SHDN 1
SHDN2
STAR TU P
UVL O
TH ER MAL
SH U TD OWN
ref (0.8 V)
FB1
0. 5V
Overload
Protection
Signal
Voltage
AGND
SHDN 1
AVIN
Reference
0. 8V
ref (0 .8V )
ref (0.8 V)
AVIN
GND 1
SS 1
EN 2
SEQ 2
SS2
Power
Sequencing 2
1V
10u
SS 2
Soft Start &
Tracking Control
(MUX2)
10u
FB2
0 .5V
180o
Error Amplifier
EOTA 2
PWM
R
SHDN1 SHDN2
SHDN 2
GND 2
TRACK 2
HS protection 2
VIN
Overload
Protection
S
CON TR OL
LOGIC 2
HS 2
COMP 2
FB 2
SW 2
pg 2
0 .9 . ref
PG 2
Delay
0 .1. ref
Falling comp
SHDN 2
Figure 2. Block Diagram
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2
NCP3120
PIN DESCRIPTION
Pin
1, 31, 32
2
−
7
8 – 10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
Symbol
SW1
V
IN
SW2
GND2
SS2
COMP2
AGND
FB2
RT
TRACK 2
TRACK 1
SEQ2
EN2
SEQ1
EN1
PG2
PG1
AV
IN
FB1
AGND
COMP1
SS1
GND1
Exposed Pad
(GND)
Description
Switch node of Channel 1. Connect an inductor between SW1 and the regulator output.
Input power supply voltage pins. These pins should be connected together to the input signal supply
voltage pin.
Switch node of Channel 2. Connect an inductor between SW2 and the regulator output.
Power ground for Channel 2
Soft−start control input for Channel 2. An internal current source charges an external capacitor connected
to this pin to set the soft−start time.
Compensation pin of Channel 2. This is the output of the error amplifier and inverting input of the PWM
comparator.
Analog ground; connect to GND1 and GND2.
Feedback Pin. Used to set the output voltage of Channel 2 with a resistive divider from the output.
Resistor select for the oscillator frequency. Connect a resistor from the RT pin to AGND to set the fre-
quency of the master oscillator. Leave this pin floating, for 200 kHz operation.
Tracking input for Channel 2. This pin allows the user to control the rise time of the second output. This pin
must be tied high in the normal operation (except in the tracking mode).
Tracking input for Channel 1. This pin allows the user to control the rise time of the first output. This pin
must be tied high in the normal operation (except in the tracking mode).
Sequence pin for Channel 2. I/O used in power sequencing. Connect SEQ to EN for normal operation of a
standalone device.
Enable input for Channel 2.
Sequence pin for Channel 1. I/O used in power sequencing. Connect SEQ to EN for normal operation of a
standalone device.
Enable input for Channel 1.
Power good, open−drain output of Channel 2. Output logic is pulled to ground when the output is less than
90% of the desired output voltage. Tied to an external pull−up resistor. Leave this pin floating, if not used.
Power good, open−drain output of Channel 1. Output logic is pulled to ground when the output is less than
90% of the desired output voltage. Tied to an external pull−up resistor. Leave this pin floating, if not used.
Input signal supply voltage pin.
Feedback Pin. Used to set the output voltage of Channel 1 with a resistive divider from the output.
Analog ground. Connect to GND1 and GND2.
Compensation pin of Channel 1. This is the output of the error amplifier and inverting input of the PWM
comparator.
Soft−start/stop control input for Channel 1. An internal current source charges an external capacitor con-
nected to this pin to set the soft−start time.
Power ground for Channel 1.
The exposed pad at the bottom of the package is the electrical ground connection of the NCP3120. This
node must be tied to ground.
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3
NCP3120
MAXIMUM RATINGS
Characteristics
Power Supply Voltage Input
Signal Supply Voltage Input
SW Pin Voltage
EN Pin Voltage Input
SEQ Pin Voltage Output
PG Pin Voltage
All Other Pins
Thermal Resistance, Junction−to−Ambient (Note 1)
Storage Temperature Range
Junction Operating Temperature (Note 2)
Symbol
V
VIN
V
AVIN
V
SW
V
EN
V
SEQ
V
PG
−
R
qJA
T
STG
T
J
Min
−0.3
−0.3
−0.7
−5V
for < 50 ns
−0.3
−0.3
−0.3
−0.3
50
−55
to +150
−40
to +150
Max
15
15
V
VIN
8.0
8.0
5.5
5.5
V
°V
°C/W
°C
°C
Unit
V
V
V
V
Stresses exceeding Maximum Ratings may damage the device. Maximum Ratings are stress ratings only. Functional operation above the
Recommended Operating Conditions is not implied. Extended exposure to stresses above the Recommended Operating Conditions may affect
device reliability.
1. R
qJA
on a 100 x 100 mm PCB with two solid 1 oz ground planes.
2. The maximum package power dissipation limit must not be exceeded
P
D
+
T
J
(max)
*
T
A
R
qJA
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NCP3120
ELECTRICAL CHARACTERISTICS
(−40°C < T
J
< 125°C, T
J
= 25°C for typical values, V
AVIN
=12 V, V
VIN
=12 V, unless otherwise
noted. R
T
= open kW)
Characteristic
RECOMMENDED OPERATING CONDITIONS
Input Voltage Range
SUPPLY CURRENT
Quiescent Supply Current
Shutdown Supply Current
UNDERVOLTAGE LOCKOUT
UVLO Threshold
UVLO Hysteresis
SWITCHING REGULATOR
Minimum Duty Cycle
Maximum Duty Cycle
High Side MOSFET R
DS(on)
High Side Leakage Current
High Side Switch Current Limit Set Point
Current Loop Transient Response
FB
V
FB
Feedback Voltage
T
J
= 25°C
T
J
=
−40
to 125°C,
4.5 V < V
IN
< 13.2V
0.788
0.784
0.8
−
0.812
0.816
V
Comp = 0.6 V
Comp = 2.6 V
I
SW
= 0.5 A, T
J
= 25°C
V
EN
= 0V, V
SW
= 0V
(Note 3)
(Note 4)
2.6
3.2
100
90
250
10
3.8
0
%
%
mW
mA
A
nsec
V
IN
Rising Edge
V
IN
Falling Edge
3.9
0.15
4.3
4.1
0.20
4.5
0.25
V
V
VEN = H, V
FB
= 1.0 V
No Switching, PG open
V
EN
= 0 V, PG open
5.0
7.0
100
mA
mA
4.5
13.2
V
Conditions
Min
Typ
Max
Unit
OSC
Oscillator Frequency
T
J
= 25°C,
T
J
=
−40
to 125°C
T
J
= 25°C, T
J
=
−40
to 125°C
(RT = 52.3 kW)
Standard Oscillator Frequency Range
TRANSCONDUCTANCE ERROR AMPLIFIER (GM)
Transconductance
DC Gain
Unity Gain Bandwidth
Output Sink Current
Output Source Current
Input Bias Current
Comp Pin Operating Voltage Range
SOFT−START
Soft−Start Period
Soft−Start Voltage Range
Soft−Start Current Source
Charging, V
SS
= 1 V
Discharging, V
SS
= 1 V
V
FB
< 0.8 V, C
S
= 0.1
mF
0
6.0
6.0
8.0
8.0
10
V
FB
12
12
ms
V
mA
mA
(Note 4)
(Note 4)
(Note 4)
V
FB
= 1.0 V, Vcomp = 1.5 V
V
FB
= 0.6 V, Vcomp = 1.5 V
V
FB
= 0.8 V
(Note 4)
0.6
80
80
0.9
50
1.0
55
4.0
100
100
100
500
2.6
1.1
60
mS
dB
MHz
mA
mA
nA
V
T
J
= 25°C
180
170
635
200
200
200
750
220
230
865
750
kHz
kHz
kHz
kHz
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