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PDF XRP7662 Data sheet ( Hoja de datos )

Número de pieza XRP7662
Descripción 12A 300KHz Synchronous Step Down Regulator
Fabricantes Exar 
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No Preview Available ! XRP7662 Hoja de datos, Descripción, Manual

XRP7662
PowerBloxTM
12A 300KHz Synchronous Step Down Regulator
September 2012
Rev. 2.2.0
GENERAL DESCRIPTION
APPLICATIONS
The XRP7662 is a synchronous voltage mode
PWM step down (buck) regulator capable of a
constant output current up to 12 Amps. A wide
5V to 22V single input voltage range allows for
single supply operations from industry
standard 5V, 12V and 18V power rails.
Operations down to 3V are supported with an
additional biasing voltage.
Distributed Power Architectures
Point of Load Converters
Power Supply Modules
FPGAs, DSPs and Processors Supplies
FEATURES
With a 300kHz constant operating frequency
and integrated high and low side switch, the
XRP7662 reduces the overall component count
and solution footprint. In addition to a 1%
output set-point accuracy, this device provides
high efficiency, low ripple and excellent line
and load regulation. An enable function and
soft start feature allow for controlled power up
sequencing implementation.
12A Continuous Current
5V-22V Single Input Voltage Rail
3V-22V Input Voltage with 5V Bias
PWM Voltage Mode Control
300kHz Fixed Synchronous Operations
Low RDSON Power Switches
0.8V Min. Output Voltage 1% Accuracy
Built-in current limiting, UVLO, output short-
circuit and over temperature protection insure
safe operation under abnormal operating
conditions.
The XRP7662 is offered in a RoHS compliant,
lead free 26-pin 7mmx4mm DFN package.
Type II & III Compensations Support
Programmable Soft Start
Over Temperature & Short Circuit
Protection/Auto-Restart
Current Limiting
RoHS Compliant Lead Free 26-Pin DFN
US Patent #6,922,041
TYPICAL APPLICATION DIAGRAM
Fig. 1: XRP7662 Application Diagram
Exar Corporation
48720 Kato Road, Fremont CA 94538, USA
www.exar.com
Tel. +1 510 668-7000 Fax. +1 510 668-7001

1 page




XRP7662 pdf
XRP7662
PowerBloxTM
12A 300KHz Synchronous Step Down Regulator
PIN DESCRIPTION
Name
PGND
GND
VFB
COMP
SS
ISN
ISP
SWN
VINP
LX
BST
VIN
UVIN
VCC
Pin Number
1-4
5,9,19,20,28
6
7
8
10
11
12
13, 29
14-16, 23-27
17
18
21
22
Description
Ground connection for the synchronous rectifier.
Ground Pin. The control circuitry of the IC and lower power driver are referenced to this
pin. Return separately from other ground traces to the (-) terminal of COUT.
Feedback Voltage and Short Circuit Detection pin. It is the inverting input of the Error
Amplifier and serves as the output voltage feedback point for the Buck Converter. The
output voltage is sensed and can be adjusted through an external resistor divider.
Whenever VFB drops 0.25V below the positive reference, a short circuit fault is detected
and the IC enters hiccup mode.
Output of the Error Amplifier. It is internally connected to the inverting input of the
PWM comparator. An optimal filter combination is chosen and connected to this pin and
either ground or VFB to stabilize the voltage mode loop.
Soft Start. Connect an external capacitor between SS and GND to set the soft start rate
based on the 10μA source current. The SS pin is held low via a 1mA (min) current
during all fault conditions.
Current sense negative input. Rail-to-rail input for over current detection.
Current sense positive input. Rail-to-rail input for over current detection.
Lower supply rail for the GH high-side gate driver. Connect this pin to the switching
node as close as possible to pins 23- 27. Do not connect this pin to pins 14 16.
Input connection to the high side N-channel MOSFET.
Connect an inductor between this pin and VOUT.
High side driver supply pin. Connect BST to the external boost diode and capacitor as
shown in the Typical Application Circuit on page 1. The high side driver is connected
between BST pin and SWN pin.
VIN connection for internal LDO and PWM Controller.
UVLO input for VIN voltage. Connect a resistor divider between VIN and UVIN to set
minimum operating voltage. Use resistor values below 20kΩ to override internal resistor
divider.
Output of internal regulator. May be externally biased if VIN < 5V. A 4.7uF or higher
ceramic capacitor should be connected to this pin close to the device.
ORDERING INFORMATION
Part Number
XRP7662IH-F
XRP7662IHTR-F
XRP7662EVB
Junction
Temperature
Range
Marking
XRP7662IH
-40°C≤TJ≤+125°C
YYWWF
X
XRP7662 Evaluation Board
Package
26-pin DFN
Packing
Quantity
Note 1
Bulk
3K/Tape & Reel Lead Free
“YY” = Year – “WW” = Work Week – “X” = Lot Number – when applicable.
Note 2
© 2012 Exar Corporation
5/19
Rev. 2.2.0

5 Page





XRP7662 arduino
XRP7662
PowerBloxTM
12A 300KHz Synchronous Step Down Regulator
Fig. 20: Over Current Detection Circuit
for IMAX>60mV/DCR
Decreasing the Current Limit
If it is required to set IMAX<(60mV/DCR), a
resistor can be added as shown in Figure 21.
R8 increases the net voltage detected by the
current-sense comparator. Voltage at the
positive and negative terminal of comparator
is given by:
Since the comparator is triggered at 60mV:
Combining the above equations and solving for
R8:
As an example: for IMAX of 12A and VOUT of
3.3V, calculated R8 is 1.5MΩ.
Fig. 21: Over Current Detection Circuit
for IMAX<(60mV/DCR)
HANDLING OF FAULTS
Upon the detection of power (UVLO), thermal,
or short-circuit faults, the XRP7662 is forced
into an idle state where the SS and COMP pins
are pulled low and both switches are held off.
In the event of UVLO fault, the XRP7662
remains in this idle state until the UVLO fault
is removed. Upon the detection of a thermal or
short-circuit fault, an internal 200ms timer is
activated. In the event of a short-circuit fault,
a restart is attempted immediately after the
120ms timeout expires. Whereas, when a
thermal fault is detected the 200ms delay
continuously recycles and a restart cannot be
attempted until the thermal fault is removed
and the timer expires.
ERROR AMPLIFIER AND VOLTAGE LOOP
The heart of the XRP7662 control loop is a
high performance, wide bandwidth
transconductance amplifier. Because of the
amplifier’s current limited (±150μA)
transconductance, there are many ways to
compensate the voltage loop or to control the
COMP pin externally. A simple, single pole,
single zero compensation can be a RC to
ground. However Exar recommends a Type II
or Type III compensation which eliminates the
gm of the amplifier from the control loop
equations. The amplifier has enough
bandwidth (45° at 4 MHz) and enough gain
(60dB) to run Type III compensation schemes
with adequate gain and phase margins at
cross over frequencies greater than 50kHz.
The common mode output of the error
amplifier is 0.9V to 2.2V. Therefore, the PWM
voltage ramp has been set between 1.1V and
2.2V to ensure proper 0% to 100% duty cycle
capability. The voltage loop also includes two
other very important features. One is a non-
synchronous startup mode. Basically, the
synchronous rectifier cannot turn on unless
the high side switch has attempted to turn on
or the SS pin has exceeded 1.7V. This feature
prevents the controller from “dragging down”
the output voltage during startup or in fault
modes.
© 2012 Exar Corporation
11/19
Rev. 2.2.0

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