XRP7674
2A 18V Synchronous PFM/PWM Step-Down Regulator
February 2013
Rev. 1.0.0
GENERAL DESCRIPTION
The XRP7674 is a 2A capable synchronous
current-mode PWM step down (buck) voltage
regulator with improved light current load
efficiency. A wide 4.5V to 18V input voltage
range allows for single supply operations from
industry standard 5V and 12V power rails.
With a 340kHz constant operating frequency
and
integrated
high
and
low-side
100mΩ/100mΩ
MOSFETs,
the
XRP7674
reduces the overall component count and
solution
footprint.
Current-mode
control
provides fast transient response and cycle-by-
cycle OCP. An adjustable soft-start prevents
inrush current at turn-on, and in shutdown
mode the supply current drops to 0.1µA. At
light current loads, the XRP7674 operates in
Discontinuous Conduction Mode (DCM) and is
complemented
by
a
pulse
frequency
modulation mode (PFM) to provide excellent
conversion efficiency.
Built-in output over-voltage (open load), over
temperature,
cycle-by-cycle
over-current,
under-voltage lockout (UVLO) and hiccup
mode short-circuit protection insures safe
operation
under
abnormal
operating
conditions.
The XRP7674 is offered in a RoHS compliant,
“green”/halogen free 8-pin SOIC package.
APPLICATIONS
Distributed Power Architecture
Portable Equipment
Point of Load Converter
Audio-Video Equipment
FEATURES
2A Continuous Output Current
4.5V to 18V Wide Input Voltage
0.925V to 16V Adjustable Output Voltage
±2% Output Voltage Accuracy
PWM Current-Mode Control
340kHz Constant Operations
Up to 95% Efficiency
Light-Load efficiency
Discontinuous Conduction Mode (DCM)
Pulse Frequency Modulation Mode (PFM)
Programmable Soft-Start and Enable
Function
Built-in Thermal, Over-Current, UVLO,
Output Over-Voltage and hiccup mode
short-circuit protection
RoHS Compliant, “Green”/Halogen
Free 8-Pin SOIC Package
TYPICAL APPLICATION DIAGRAM
Fig. 1: XRP7674 Application Diagram
Exar Corporation
48720 Kato Road, Fremont CA 94538, USA
www.exar.com
Tel. +1 510 668-7000 – Fax. +1 510 668-7001
XRP7674
2A 18V Synchronous PFM/PWM Step-Down Regulator
ABSOLUTE MAXIMUM RATINGS
These are stress ratings only and functional operation of
the device at these ratings or any other above those
indicated in the operation sections of the specifications
below is not implied. Exposure to absolute maximum
rating conditions for extended periods of time may affect
reliability.
Supply Voltage V
IN
...................................... -0.3V to 20V
Switch Node Voltage V
SW
......................................... 21V
Boost Voltage V
BS
................................... -0.3 to V
SW
+6V
Enable Voltage V
EN
......................................... -0.3 to V
IN
All Other Pins .............................................. -0.3 to +6V
Junction Temperature .......................................... 150°C
Storage Temperature .............................. -65°C to 150°C
Lead Temperature (Soldering, 10 sec) ................... 260°C
ESD Rating (HBM - Human Body Model) .................... 2kV
ESD Rating (MM - Machine Model) ...........................200V
Moisture Sensitivity Level (MSL) ................................... 3
OPERATING RATINGS
Input Voltage V
IN
......................................... 4.5V to 18V
Ambient Operating Temperature ................ -40°C to 85°C
Maximum Output Current.................................... 2A min
Thermal Resistance θ
JA
.....................................105°C/W
ELECTRICAL SPECIFICATIONS
Specifications are for an Operating Ambient Temperature of T
A
= 25°C only; limits applying over the full Ambient Operating
Temperature range are denoted by a “•”. Minimum and Maximum limits are guaranteed through test, design, or statistical
correlation. Typical values represent the most likely parametric norm at T
A
= 25°C, and are provided for reference purposes
only. Unless otherwise indicated, V
IN
= V
EN
= 12V, V
OUT
=3.3V.
Parameter
Shutdown Supply Current
Quiescent Current
Feedback Voltage V
FB
Feedback Overvoltage Threshold
Feedback Bias Current
Error Amplifier Voltage Gain A
EA
Error Amplifier
Transconductance G
EA
COMP to Current Sense
Transconductance G
CS
High-Side switch On Resistance
R
DSONH2
Low-Side switch On Resistance
R
DSONL2
High-Side switch Leakage
Current
High-Side Switch Current Limit
Low-Side Switch Current Limit
Oscillator Frequency F
OSC1
Short Circuit Oscillator
Frequency F
OSC2
Maximum Duty Cycle D
MAX
Minimum Duty Cycle D
MIN
Minimum Start-up Current
Minimum No Load Start-up
Voltage
Minimum Full Load Start-up
Voltage
10
5
4.75
280
2.7
1
Min.
Typ.
0.1
1.2
Max.
10
1.4
0.943
0.1
Units
µA
mA
V
V
µA
V/V
µA/V
A/V
mΩ
mΩ
V
FB
=1V
V
EN
=0V
Conditions
V
EN
=3V, V
FB
=1V
0.907
-0.1
0.925
1.1
400
800
3.5
100
100
0.1
3.5
0
340
90
90
I
SW
=0.2A&0.7A
I
SW
=-0.2A&-0.7A
V
IN
=18V, V
EN
=0V, V
SW
=0V
Drain to Source
10
µA
A
A
400
kHz
kHz
%
V
FB
=0.85V
V
FB
=1V
V
IN
≤4.75V
I
OUT
=0A
I
OUT
=2A
0
%
mA
V
V
© 2013 Exar Corporation
2/12
Rev. 1.0.0
XRP7674
2A 18V Synchronous PFM/PWM Step-Down Regulator
Parameter
EN Shutdown Threshold
EN Shutdown Hysteresis
EN Lockout Threshold
EN Lockout Hysteresis
UVLO Threshold
UVLO Hysteresis
Soft-start Current
Soft-start Time
1
1
1
1
Min.
1.1
2.2
3.65
Typ.
1.5
0.35
2.5
0.21
4.00
0.20
5
15
160
30
Max.
2
2.7
4.25
Units
V
V
V
V
µA
ms
°C
°C
V
IN
Rising
Conditions
C
SS
=0.1µF, I
OUT
=500mA
Thermal Shutdown
Thermal Shutdown Hysteresis
Note 1: Guaranteed by design.
Note 2: R
DSON
=(V
SW1
-V
SW2
)/(I
SW1
-I
SW2
)
BLOCK DIAGRAM
Fig. 2: XRP7674 Block Diagram
© 2013 Exar Corporation
3/12
Rev. 1.0.0
XRP7674
2A 18V Synchronous PFM/PWM Step-Down Regulator
PIN ASSIGNMENT
Fig. 3: XRP7674 Pin Assignment (SOIC-8)
PIN DESCRIPTION
Name
BS
Pin Number
1
Description
Bootstrap pin.
Connect a 0.01µF or greater bootstrap capacitor between the BS pin and the SW pin.
The voltage across the bootstrap capacitor drives the internal high-side power MOSFET.
Power input pin.
A capacitor should be connected between the IN pin and GND pin to keep the input
voltage constant.
Power switch output pin.
This pin is connected to the inductor and the bootstrap capacitor.
Ground pin.
Feedback pin.
An external resistor divider connected to FB programs the output voltage. If the
feedback pin exceeds 1.1V the over-voltage protection will trigger. If the feedback
voltage drops below 0.3V the oscillator frequency is lowered to achieve short-circuit
protection.
Compensation pin.
This is the output of transconductance error amplifier and the input to the current
comparator. It is used to compensate the control loop. Connect an RC network form
this pin to GND.
Control input pin.
Drive EN high/low in order to turn on/off the regulator. When the IC is in shutdown
mode all functions are disabled to decrease the supply current below 1µA. This input
can be connected to VIN (pin 2) through a 100kΩ resistor for automatic startup
operations.
Soft-start control input pin.
Connect a capacitor from SS to GND to set the soft-start period. A 0.1µF capacitor sets
the soft start period to 15ms. To disable the soft-start feature, leave SS unconnected.
IN
SW
GND
2
3
4
FB
5
COMP
6
EN
7
SS
8
ORDERING INFORMATION
Part Number
XRP7674IDTR-F
XRP7674EVB
Temperature
Range
-40°C≤T
A
≤+85°C
Marking
Package
SOIC-8
Packing
Quantity
Note 1
Note 2
XRP7674I
YYWWF
X
XRP7674 Evaluation Board
2.5K/Tape & Reel RoHS Compliant
Halogen Free
“YY” = Year – “WW” = Work Week – “X” = Lot Number; when applicable.
© 2013 Exar Corporation
4/12
Rev. 1.0.0
XRP7674
2A 18V Synchronous PFM/PWM Step-Down Regulator
TYPICAL PERFORMANCE CHARACTERISTICS
All data taken at V
IN
= 12V, V
OUT
=3.3V, T
J
= T
A
= 25°C, unless otherwise specified - Schematic and BOM from Application
Information section of this datasheet.
Fig. 4: Efficiency versus output current
Fig. 5: Quiescent current versus temperature
Fig. 6: Feedback voltage versus temperature
Fig. 7: Output voltage versus load current
Fig. 8: Output voltage versus input voltage
Fig. 9: Minimum Start-Up Voltage vs Output Current
© 2013 Exar Corporation
5/12
Rev. 1.0.0
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