XRP6658
1A 1.5MHz PFM/PWM Synchronous Step-Down Converter
January 2014
Rev. 1.6.0
GENERAL DESCRIPTION
APPLICATIONS
The XRP6658 is a synchronous current mode
PWM step down (buck) converter capable of
delivering up to 1 Amp of current and
optimized
for
portable
battery-operated
applications.
Based on a current mode 1.5MHz constant
frequency PWM control scheme, the XRP6658
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 XRP6658 is offered in a RoHS compliant,
“green”/halogen free 5-pin SOT23 package.
• Portable Equipments
• Battery Operated Equipments
• Audio-Video Equipments
• Networking & Telecom Equipments
FEATURES
• Guaranteed 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
− Achieves 97% Efficiency
• Adjustable Output Voltage Range
− As Low as 0.6V with ±3% Accuracy
• Internal Compensation Network
• 15µA Quiescent Current
• Over Temperature & UVLO Protections
• RoHS Compliant “Green”/Halogen Free
5-Pin SOT23 Package
TYPICAL APPLICATION DIAGRAM
Fig. 1: XRP6658 Application Diagram
Exar Corporation
48720 Kato Road, Fremont CA 94538, USA
www.exar.com
Tel. +1 510 668-7000 – Fax. +1 510 668-7001
XRP6658
1A 1.5MHz PFM/PWM Synchronous Step-Down Converter
ABSOLUTE MAXIMUM RATINGS
OPERATING 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.
Input Voltage Range VIN ............................... 2.5V to 5.5V
Ambient Temperature Range TA ................ -40°C to 85°C
Junction Temperature Range TJ.................-40°C to 125°C
Thermal Resistance ......................................................
θJA (5 Pin SOT23) ....................................... 134.5°C/W
θJC (5 Pin SOT23) ........................................... 81°C/W
Input Voltage VIN ...................................... -0.3V to 6.0V
EN, VFB Voltages .......................................... -0.3V to VIN
SW Voltage .................................... -0.3V to (VIN + 0.3V)
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
Junction Temperature (Notes 1, 3) ....................... 150°C
ELECTRICAL SPECIFICATIONS
Specifications are for an Ambient Temperature of TA = 25°C only; limits applying over the full 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 TA = 25°C, and are provided for reference purposes only. Unless
otherwise indicated, VIN = 3.6V, TA= 25°C.
Parameter
Input Voltage Range
Min.
Typ.
2.5
Feedback Current
Regulated Feedback Voltage
Units
5.5
V
+100
nA
0.612
V
Output Voltage Accuracy
-3
+3
%
Output Voltage Accuracy
-3
+3
%
Reference Voltage Line Regulation
0.4
%/V
Reference Voltage Line Regulation
0.4
%/V
Output Voltage Line Regulation
0.4
%/V
Output Voltage Line Regulation
0.4
%/V
Peak Inductor Current
0.588
1.5
PWM Quiescent Current (Note 2)
PFM Quiescent Current
Shutdown
Oscillator Frequency
1.2
0.600
Max.
Conditions
IOUT=100mA, VIN = 2.5V to 3.0V
• IOUT=100mA, VIN = 3.0V to 5.5V
VIN = 2.5V to 3.0V
• VIN = 3.0V to 5.5V
VIN = 2.5V to 3.0V
• VIN = 3.0V to 5.5V
2.3
A
188
µA
VFB = 0.5V or VOUT = 90%
15
µA
VFB = 0.65V or VOUT = 108%
0.1
1
µA
1.5
1.8
MHz
VFB = 0.5V or VOUT = 90%
VRUN = 0V, VIN = 4.2V
• VFB = 0.6V or VOUT = 100%
• VFB = 0V or VOUT = 0V
Short-Circuit Oscillator Frequency
900
kHz
RDS(ON) of PMOS
0.24
Ω
ISW = 100mA
RDS(ON) of NMOS
0.21
Ω
ISW = –100mA
Under Voltage Lock Out
1.8
V
SW Leakage
+1
µA
Enable Threshold
1.2
V
V
•
+1
µA
•
Shutdown Threshold
EN Leakage Current
0.4
VRUN = 0V, VSW = 0V or 5V, VIN = 5V
•
Note 1: TJ is a function of the ambient temperature TA and power dissipation PD: (TJ = TA + (PD * θJA))
Note 2: Dynamic quiescent current is higher due to the gate charge being delivered at the switching frequency.
Note 3: This IC is built-in over-temperature protection to avoid damage from overload conditions.
Note 4: θJA is measured in the natural convection at TA=25℃ on a high effective thermal conductivity test board (2 layers,
2S0P) of JEDEC 51-5 thermal measurement standard.
Note 5: θJC represents the resistance to the heat flows the chip to package top case.
© 2014 Exar Corporation
2/11
Rev. 1.6.0
XRP6658
1A 1.5MHz PFM/PWM Synchronous Step-Down Converter
BLOCK DIAGRAM
Fig. 2: XRP6658 Block Diagram
PIN ASSIGNMENT
Fig. 3: XRP6658 Pin Assignment
© 2014 Exar Corporation
3/11
Rev. 1.6.0
XRP6658
1A 1.5MHz PFM/PWM Synchronous Step-Down Converter
PIN DESCRIPTION
Name
Pin Number
Description
VIN
1
GND
2
Ground Signal
EN
3
Enable Pin.
Minimum 1.2V to enable the device. Maximum 0.4V to shutdown the device.
VFB
4
Feedback Pin.
Receives the feedback voltage from an external resistive divider across the output.
SW
5
Switch Pin.
Must be connected to Inductor. This pin connects to the drains of the internal main and
synchronous power MOSFET switches.
Power Input Pin.
Must be closely decoupled to GND pin with a 4.7µF or greater ceramic capacitor.
ORDERING INFORMATION
Part Number
XRP6658ISTR-F
XRP6658EVB
Temperature
Range
Marking
Package
Packing
Quantity
-40°C≤TJ≤+125°C
HCWW
5-Pin SOT23
3K/Tape & Reel
Note 1
Note 2
RoHS Compliant
Halogen Free
XRP6658 Evaluation Board
“WW” = Work Week
Note that the XRP6658 series is packaged in Tape and Reel with a reverse part orientation as per
the following diagram
© 2014 Exar Corporation
4/11
Rev. 1.6.0
XRP6658
1A 1.5MHz PFM/PWM Synchronous Step-Down Converter
TYPICAL PERFORMANCE CHARACTERISTICS
All data taken at VIN = 3.6V, TJ = TA = 25°C, unless otherwise specified - Schematic and BOM from Application Information
section of this datasheet.
Fig. 4: Efficiency vs Output Current (VOUT=3.3V)
Fig. 5: Efficiency vs Output Current (VOUT=1.2V)
Fig. 6: Oscillator Frequency vs Temperature
Fig. 7: Oscillator Frequency vs Supply Voltage
Fig. 8: RDS(ON) vs Temperature
Fig. 9: RDS(ON) vs Input Voltage
© 2014 Exar Corporation
5/11
Rev. 1.6.0
XRP6658
1A 1.5MHz PFM/PWM Synchronous Step-Down Converter
Fig. 10: EN Pin Threshold vs Temperature
Fig. 11: UVLO Threshold vs Temperature
Fig. 12: Quiescent Current vs Temperature (PFM Mode)
Fig. 13: Quiescent Current vs Input Voltage (PFM Mode)
Fig. 14: Current Limit vs Temperature (VOUT=1.2V)
Fig. 15: Current Limit vs Input Voltage (VOUT=1.2V)
© 2014 Exar Corporation
6/11
Rev. 1.6.0
XRP6658
1A 1.5MHz PFM/PWM Synchronous Step-Down Converter
Fig. 16: Power On From EN Pin (IOUT=1A)
Fig. 17: Power On From EN Pin (IOUT=10mA)
Fig. 18: Power On From VIN (IOUT=1A)
Fig. 19: Power Off From EN (IOUT=1A)
Fig. 20: Load Step Response
VOUT=1.2V, IOUT From 50mA to 500mA
Fig. 21: Load Step Response
VOUT=1.2V, IOUT From 50mA to 1A
© 2014 Exar Corporation
7/11
Rev. 1.6.0
XRP6658
1A 1.5MHz PFM/PWM Synchronous Step-Down Converter
It is recommended to use X5R or X7R ceramic
capacitors as they have the best temperature
and voltage characteristics.
THEORY OF OPERATION
The typical application circuit of adjustable
version is shown in figure 22.
OUTPUT VOLTAGE SELECTION
The output voltage is adjustable via the
external resistor network R1 and R2 as per the
following formula:
Fig. 22: Typical Application
THERMAL CONSIDERATIONS
The inductor value L can be calculated from
the following equation:
x
Although thermal shutdown is built-in in
XRP6658 to protect the device from thermal
damage, the total power dissipation that
XRP6658 can sustain is based on the package
thermal capability. The formula to ensure safe
operation is shown in Note 1. To avoid
XRP6658 from exceeding the maximum
junction temperature, some thermal analysis
is required.
1
x
∆
CIN AND COUT SELECTION
A low ESR input capacitor can minimize the
input voltage ripple. Voltage rating of the
capacitor should be at least 50% higher than
the input voltage. The RMS current of the
input capacitor is required to be larger than
the IRMS calculated by:
≅
-
GUIDELINES FOR PCB LAYOUT
To ensure proper operation of the XRP6658,
please note the following PCB layout
guidelines:
1. The GND, SW and VIN traces should be
kept short, direct and wide.
The ESR value is an important parameter to
consider when selecting an output capacitor
COUT. The output ripple VOUT is determined by:
∆
≅ ∆IL ESR"
1
8 f %
2. VFB pin must be connected directly to the
feedback resistors. Resistive divider R1/R2
must be connected in parallel to the output
capacitor COUT.
The output capacitor’s value can be optimized
for very low output voltage ripple and small
circuit size. Voltage rating of the capacitor
should be at least 50% higher than the output
voltage. Higher values, lower cost ceramic
capacitors are now available in smaller sizes.
These ceramic capacitors have high ripple
currents, high voltage ratings and low ESR
that make them ideal for switching regulator
applications.
© 2014 Exar Corporation
R2
R1
The feedback resistors must be chosen such
that power dissipation of the network is
minimal. R1 must be selected within the range
of 80kΩ≤ R1 ≤120kΩ. R2 is selected based on
the above equation.
Inductor ripple current and saturation current
rating are two factors to be considered when
selecting the inductor value. A low DCR
inductor is preferred.
1
1"
where, VREF is the reference voltage at 0.6V.
INDUCTOR SELECTION
&'
3. The input capacitor CIN must be as close as
possible to pin VIN.
4. Keep SW node away from the sensitive VFB
node since SW signal experiences high
frequency voltage swings.
8/11
Rev. 1.6.0
XRP6658
1A 1.5MHz PFM/PWM Synchronous Step-Down Converter
TYPICAL APPLICATIONS
Fig. 23: 3.3V/5.5V to 3.3V Conversion
Fig. 24: 2.5V/5.5V to 1.2V Conversion
© 2014 Exar Corporation
9/11
Rev. 1.6.0
XRP6658
1A 1.5MHz PFM/PWM Synchronous Step-Down Converter
PACKAGE SPECIFICATION
5-PIN SOT23
© 2014 Exar Corporation
10/11
Rev. 1.6.0
XRP6658
1A 1.5MHz PFM/PWM Synchronous Step-Down Converter
REVISION HISTORY
Revision
Date
Description
1.0.0
09/16/2010
Initial release of datasheet
1.1.0
09/30/2010
Corrected pin-out on schematics Figures 1, 23 and 24
1.2.0
11/15/2010
Corrected ∆
equation: changed
to %
. Updated ‘Output Voltage selection’ section.
1.3.0
01/14/2011
Added specific test conditions and data in Electrical Specification Table for output voltage
accuracy, reference voltage Line regulation and output voltage line regulation for operations
below 3V.
1.4.0
07/19/2011
Corrected typographical errors on package specification table parameters “b” and “e”
1.5.0
0/15/2011
1.6.0
1/13/2014
Added a range for the selection of lower feedback resistor.
Added “Junction Temperature Range TJ……-40°C to 125°C” to operating ratings;
In “Ordering Information” changed the temperature range to “-40°C≤TJ≤+125°C”
[ECN: 1403-04]
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
malfunction of the product can reasonably be expected to cause failure of the life support system or to significantly affect
safety or effectiveness. Products are not authorized for use in such applications unless EXAR Corporation receives,
writing, assurances to its satisfaction that: (a) the risk of injury or damage has been minimized; (b) the user assumes
such risks; (c) potential liability of EXAR Corporation is adequately protected under the circumstances.
or
its
in
all
Reproduction, in part or whole, without the prior written consent of EXAR Corporation is prohibited.
© 2014 Exar Corporation
11/11
Rev. 1.6.0
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