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February 2012
Rev. 1.1.0
Exar Corporation www.exar.com
48720 Kato Road, Fremont CA 94538, USA Tel. +1 510 668-7000 – Fax. +1 510 668-7001
GENERAL DESCRIPTION
The XRP6668 is a dual channel synchronous
current mode PWM step down (buck)
converter capable of delivering up to 1 Amp of
current per channel and optimized for portable
battery-operated applications.
Based on a current mode 1.5MHz constant
frequency PWM control scheme, the XRP6668
reduces the overall component count and
solution footprint as well as provides a low
output voltage ripple and excellent line and
load regulation. It also implements a PFM
mode to improve light load efficiency as well
as a 100% duty cycle LDO mode. Output
voltage is adjustable to as low as 0.6V with a
better than 3% accuracy while a low quiescent
current supports the most stringent battery
operating conditions.
Built-in over temperature and under voltage
lock-out protections insure safe operations
under abnormal operating conditions.
The XRP6668 is offered in a RoHS compliant,
“green”/halogen free 8-pin exposed pad SOIC
package.
E
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AT
TI
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ON
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B
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FEATURES
Dual Channel Step Down Converter
Guaranteed Dual 1A/1A Output Current
Input Voltage: 2.5V to 5.5V
1.5MHz PWM Current Mode Control
PFM Mode Operations at Light Load
100% Duty Cycle LDO Mode Operations
Adjustable Output Voltage Range
Internal Compensation Network
30µA Quiescent Current
Over Temperature & UVLO Protections
EVALUATION BOARD SCHEMATICS
Fig. 1: XRP6658EVB Evaluation Board Schematics
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© 2012 Exar Corporation 2/7 Rev. 1.1.0
PIN ASSIGNMENT
Fig. 2: XRP6658 Pin Assignment
PIN DESCRIPTION
Name
Pin Number
Description
VIN1
1
Channel 1 Power Input Pin.
Must be closely decoupled to GND pin with a 4.7μF or greater ceramic capacitor.
SW1
2
Channel 1 Switch Pin.
Must be connected to Inductor. This pin connects to the drains of the internal main and
synchronous power MOSFET switches.
VIN2
3
Channel 2 Power Input Pin.
Must be closely decoupled to GND pin with a 4.7μF or greater ceramic capacitor.
SW2
4
Channel 2 Switch Pin. Must be connected to Inductor. This pin connects to the drains of
the internal main and synchronous power MOSFET switches.
VFB2
5
Channel 2 Feedback Pin.
Receives the feedback voltage from an external resistive divider across the output.
EN2
6
Channel 2 Enable Pin.
Minimum 1.2V to enable the device. Maximum 0.4V to shutdown the device.
VFB1
7
Channel 1 Feedback Pin.
Receives the feedback voltage from an external resistive divider across the output.
EN1
8
Channel 1 Enable Pin.
Minimum 1.2V to enable the device. Maximum 0.4V to shutdown the device.
GND
Exposed Pad
Connect to GND.
ORDERING INFORMATION
Refer to XRP6668’s datasheet and/or www.exar.com for exact and up to date ordering information.
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© 2012 Exar Corporation 3/7 Rev. 1.1.0
USING THE EVALUATION BOARD
INITIAL SETUP
Set the input supply to a voltage between
2.5V to 5.5V and connect it to VIN and GND
connectors on the left side of the evaluation
board. Connect the load to the VOUT and GND
connectors on the right hand side of the
board. Check to make sure that jumper J1 is
set to VIN. The board will power-up and
regulate to the desired output voltage VOUT
set by the feedback resistors. The board will
operate with a load current IOUT of up to 1A
and provide efficiency equal to figures 4 and 5
of XRP6658 datasheet.
JUMPER J1 FUNCTION
Jumper J1 can be used to either short EN pin
to VIN or to GND. The Board is supplied from
EXAR with the jumper set to connect EN to
VIN.
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© 2012 Exar Corporation 4/7 Rev. 1.1.0
EVALUATION BOARD SCHEMATICS
VIN = 2.5V - 5.5V
VIN = 3.3V - 5.5V
VIN2
VOUT = 3.3V
VOUT = 1.8V
FB1
U1 XRP6668
SW2
4
SW1
2VIN1
1EN1 8
EN2 6
VFB1 7
VFB2 5
VIN2
3
GND
9
L1
2.2uH
L2
2.2uH
C5
4.7uF
C1
4.7uF
FB2
R1
20
R2
453k R3
100k
C6
10uF
C2
10uF
EN1
SW1
R5
200k
R4
20
EN2
R6
100k
SW2
C10
NP
GND
GND
J1
1 3
2
R7
NP
R8
NP
R9
NP R10
NP
J2
1 3
2
C3
22pF
GND
C7
22pF
C9
NP
GND
VIN1
VIN2
C4
NP
VOUT1
GND
VOUT2
C8
NP
VIN1
T2
GND
T1
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© 2012 Exar Corporation 5/7 Rev. 1.1.0
BILL OF MATERIAL
Qty
Manufacturer
Part Number
Size
Component
1
Exar Corp
XRP6668EVB
XRP6668 Evaluation Board
1
Exar Corp
XRP6668
ESOP-8L
Synchronous Step-Down Regulator
2
Murata
GRM21BR71C475KA73L
0805
Ceramic 4.7µF, 16V, X7R
2
Not populated
2
Murata
GRM21BR71A106KE51L
0805
Ceramic 10uF, 10V, X7R
2
Not populated
2
Murata
GRM1885C1H220JA01D
0603
Ceramic 22pF, 50V, C0G
2
Wurth Electronik
7440430022
4.8mm x
4.8mm x
2.8mm
Inductor 2.2uH, 2.5A, 23mΩ
2
Vishay
CRCW060320R0FKTA
0603
20Ω Resistor, 0.1W, 1%
1
Vishay
CRCW0603453KFKTA
0603
453KΩ Resistor, 0.1W, 1%
1
Vishay
CRCW0603200KFKTA
0603
200KΩ Resistor, 0.1W, 1%
2
Vishay
CRCW0603100KFKTA
0603
100KΩ Resistor, 0.1W, 1%
2
Wurth Electronik
61303611121
0.64mm SQ x
6mm
3 Pin Header, 2.54mm pitch
2
Wurth Electronik
609002115121
0.1”
Jumper short
16
Mill-Max
0300-115-01-4727100
0.042”
diameter
Test Point Post
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© 2012 Exar Corporation 6/7 Rev. 1.1.0
EVALUATION BOARD LAYOUT
Fig. 3: Component Placement – Top Side
Fig. 4: Component Placement 2 – Top Side
Fig. 5: Layout – Top Side
Fig. 6: Layout - Bottom
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© 2012 Exar Corporation 7/7 Rev. 1.1.0
REVISION HISTORY
Revision
Date
Description
1.0.0
09/16/2010
Initial release of document
1.1.0
02/07/2012
Updated bill of material and schematics
FOR FURTHER ASSISTANCE
Email: customersupport@exar.com
Exar Technical Documentation: http://www.exar.com/TechDoc/default.aspx?
EXAR CORPORATION
HEADQUARTERS AND SALES OFFICES
48720 Kato Road
Fremont, CA 94538 – USA
Tel.: +1 (510) 668-7000
Fax: +1 (510) 668-7030
www.exar.com
NOTICE
EXAR Corporation reserves the right to make changes to the products contained in this publication in order to improve
design, performance or reliability. EXAR Corporation assumes no responsibility for the use of any circuits described herein,
conveys no license under any patent or other right, and makes no representation that the circuits are free of patent
infringement. Charts and schedules contained here in are only for illustration purposes and may vary depending upon a
user’s specific application. While the information in this publication has been carefully checked; no responsibility, however,
is assumed for inaccuracies.
EXAR Corporation does not recommend the use of any of its products in life support applications where the failure or
malfunction of the product can reasonably be expected to cause failure of the life support system or to significantly affect its
safety or effectiveness. Products are not authorized for use in such applications unless EXAR Corporation receives, in
writing, assurances to its satisfaction that: (a) the risk of injury or damage has been minimized; (b) the user assumes all
such risks; (c) potential liability of EXAR Corporation is adequately protected under the circumstances.
Reproduction, in part or whole, without the prior written consent of EXAR Corporation is prohibited.