B130 [EXAR]
3A 18V Synchronous Step-Down Converter; 3A 18V同步降压转换器
| 型号： | B130 |
| 厂家： | 
EXAR CORPORATION |
| 描述： | 3A 18V Synchronous Step-Down Converter |
| 文件： | 总12页 (文件大小：759K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
XRP7665
3A 18V Synchronous Step-Down Converter
March 2013
Rev. 2.0.1
GENERAL DESCRIPTION
APPLICATIONS
The XRP7665 is a synchronous current-mode
PWM step down (buck) regulator capable of a
constant output current up to 3 Amps. A wide
4.50V to 18V input voltage range allows for
single supply operations from industry
standard 5V and 12V power rails.
ñ Distributed Power Architectures
ñ Point of Load Converters
ñ Audio-Video Equipments
ñ Medical & Industrial Equipments
With a 340kHz constant operating frequency
FEATURES
and
integrated
high
and
low
side
100 mΩ9/0 mΩ MOS F,EthTesXRP7665 reduces
the overall component count and solution
footprint. Current-mode control provides fast
transient response and cycle-by-cycle current
limit. An adjustable soft-start prevents inrush
current at turn-on, and in shutdown mode the
supply current drops to 0.1µA.
ñ Pin/Function Compatible to MP1484
ñ 3A Continuous Output Current
ñ 4.50V to 18V Wide Input Voltage
ñ PWM Current Mode Control
- 340kHz Constant Operations
- Up to 93% Efficiency
Built-in output over voltage (open load), over
temperature, cycle-by-cycle over current and
under voltage lockout (UVLO) protections
insure safe operations under abnormal
operating conditions.
ñ Adjustable Output Voltage
- 0.925V to 16V Range
- 2.0% Accuracy
ñ Programmable Soft-Start and Enable
The XRP7665 is a pin and function compatible
device to MP1484 and a 3A pin to pin upgrade
to XRP7664.
Function
ñ Built-in Thermal, Over Current, UVLO
and Output Over Voltage Protections
The XRP7665 is offered in a RoHS compliant,
“ g r e e n ” / h a l o-gpiennexpofsredepead S8OIC
package.
ñ R o HS C o mp l i a n t
“ Gr e e n ” / Ha l o g
8-Pin Exposed Pad SOIC Package
TYPICAL APPLICATION DIAGRAM
Fig. 1: XRP7665 Application Diagram
Exar Corporation
48720 Kato Road, Fremont CA 94538, USA
www.exar.com
Tel. +1 510 668-7000 – Fax. +1 510 668-7001
XRP7665
3A 18V 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 VIN .......................................4.50V to 18V
Ambient Operating Temperature................ -40°C to 85°C
Maximum Output Current.................................... 3A min
T h e r ma l
R e s JiA .s...t...a...n..c...e......θ................. 60°C/W
Supply Voltage VIN......................................-0.3V to 20V
Switch Node Voltage VSW ......................................... 21V
Boost Voltage VBS ................................... -0.3 to VSW+6V
Enable Voltage VEN......................................... -0.3 to VIN
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
ELECTRICAL SPECIFICATIONS
Specifications are for an Operating Ambient Temperature of TA = 25°C only; limits applying over the full Ambient Operating
Te mp e r a t u r e r a n g e a r e d e n o t e d b y “ • ” . Mi n i mduthmrouaghntdest,Mdeasxigni ,morusmtatisltiicaml i t s
a
a r e
correlation. Typical values represent the most likely parametric norm at TA = 25°C, and are provided for reference purposes
only. Unless otherwise indicated, VIN = VEN = 12V, VOUT=3.3V.
Parameter
Min.
Typ.
Max.
Units
Conditions
Shutdown Supply Current
Quiescent Current
0.1
1.2
10
1.4
µA
mA
V
VEN≤0.75V
VEN=3V, VFB=1V
Feedback Voltage VFB
0.925
1.1
0.943
0.907
-0.1
Feedback Overvoltage Threshold
Feedback Bias Current
V
0.1
µA
VFB=1V
Error Amplifier Voltage Gain AEA
(Note 1)
400
800
100
100
0.1
V/V
µA/V
mΩ
mΩ
µA
Error Amplifier
Transconductance GEA
High-Side switch On Resistance
RDSONH (Note 2)
ISW=0.2A&0.7A
Low-Side switch On Resistance
RDSONL (Note 2)
ISW=-0.2A&-0.7A
High-Side switch Leakage
Current
10
VIN=18V, VEN=0V, VSW=0V
High-Side Switch Current Limit
Low-Side Switch Current Limit
5.6
1.4
A
A
4.3
From Drain to Source
COMP to Current Sense
Transconductance GCS
5.2
340
90
A/V
kHz
kHz
Oscillator Frequency FOSC1
400
280
Short Circuit Oscillator
Frequency FOSC2
Maximum Duty Cycle DMAX
Minimum Duty Cycle DMIN
EN Enable Threshold Voltage
90
%
%
V
VFB=0.85V
VFB=1V
0
2.5
210
4.00
2.7
2.2
EN Enable Threshold Voltage
Hysteresis (Note 1)
mV
V
UVLO Threshold
4.25
VIN Rising
3.65
© 2013 Exar Corporation
2/12
Rev. 2.0.1
XRP7665
3A 18V Synchronous Step-Down Converter
Parameter
UVLO Hysteresis
Min.
Typ.
Max.
Units
Conditions
0.20
6
V
Soft-start Current
µA
ms
°C
VSS=0V
Soft-start Time (Note 1)
Thermal Shutdown (Note 1)
15
CSS=0.1µF
160
Thermal Shutdown Hysteresis
(Note 1)
20
°C
Note 1: Guaranteed by design.
Note 2: RDSON=(VSW1-VSW2)/(ISW1-ISW2
)
BLOCK DIAGRAM
Fig. 2: XRP7665 Block Diagram
PIN ASSIGNMENT
Fig. 3: XRP7665 Pin Assignment (SOIC-8 Exposed Pad)
3/12
© 2013 Exar Corporation
Rev. 2.0.1
XRP7665
3A 18V Synchronous Step-Down Converter
PIN DESCRIPTION
Name
Pin Number
Description
Bootstrap pin.
1
2
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.
BS
Power input pin.
A capacitor should be connected between the IN pin and GND pin to keep the input
voltage constant.
IN
Power switch output pin.
This pin is connected to the inductor and the bootstrap capacitor.
3
4
SW
Ground signal pin.
GND
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.
5
FB
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.
6
7
COMP
EN
Control input pin.
Forcing this pin above 2.7V enables the IC. Forcing this pin below 0.75V shuts down the
I C .
P u l l
u p t o V I N wi t h 1 0 0 k Ω f o r
a u t o ma t i c
s
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.
8
SS
-
Exposed Pad
Connect to GND through PCB.
EP
ORDERING INFORMATION
Temperature
Part Number
Packing
Quantity
Marking
Package
Note 1
Note 2
Range
XRP7665I
YYWWF
X
RoHS Compliant
Halogen Free
2.5K/Tape & Reel
XRP7665IDBTR-F
XRP7665EVB
SOIC-8(EP)
-4 0 ° C A≤≤T+8 5 ° C
XRP7665 Evaluation Board
“ Y Y ”
= –Y“ eWaWr”
=
Wo r k– “WXe”e k= L o t ; wNhuenmabpeplircable.
© 2013 Exar Corporation
4/12
Rev. 2.0.1
XRP7665
3A 18V Synchronous Step-Down Converter
TYPICAL PERFORMANCE CHARACTERISTICS
All data taken at VIN = 12V, VOUT=3.3V, TJ = TA = 25°C, unless otherwise specified - Schematic and BOM from Application
Information section of this datasheet.
Fig. 5: RDSONH versus case temperature
Fig. 7: Feedback voltage versus case temperature
Fig. 9: Output voltage versus output current
Fig. 4: Efficiency versus output current
Fig. 6: RDSONL versus case temperature
Fig. 8: Quiescent current versus case temperature
© 2013 Exar Corporation
5/12
Rev. 2.0.1
XRP7665
3A 18V Synchronous Step-Down Converter
Fig. 10: Output voltage ripple, IOUT=3A
Fig. 11: Load transient (IOUT=1.5A to 3A)
Fig. 12: Enable turn on
Fig. 13: Enable turn off
CC mode, VIN=12V, VOUT=VEN=3.3, IOUT=3A
CC mode, VIN=12V, VOUT=VEN=3.3, IOUT=3A
Fig. 14: Short-circuit protection
Fig. 15: Short-circuit recovery
© 2013 Exar Corporation
6/12
Rev. 2.0.1
XRP7665
3A 18V Synchronous Step-Down Converter
THEORY OF OPERATION
OVERCURRENT PROTECTION OCP
The OCP protects against accidental increase
in load current that can cause the regulator to
FUNCTIONAL DESCRIPTION
fail. The current of internal switch M1 is
monitored. If this current reaches 5.6A then
M1 is turned off until next switching cycle.
The XRP7665 is a synchronous, current-mode,
step-down regulator. It regulates input
voltages from 4.5V to 18V and supplies up to
3A of continuous load current. The XRP7665
uses current-mode control to regulate the
output voltage. The output voltage is
measured at FB through a resistive voltage
divider and input to a transconductance error
amplifier. The high-side switch current is
compared to the output of the error amplifier
to control the output voltage. The regulator
utilizes internal N-channel MOSFETs to step-
down the input voltage. A bootstrapping
capacitor connected between BS and SW acts
as a supply for high-side MOSFET. This
capacitor is charged from the internal 5V
supply when SW node is low. The XRP7665
has several powerful protection features
including OCP, OVP, OTP, UVLO and output
short-circuit.
SHORT-CIRCUIT PROTECTION
If there is short-circuit across the output, the
feedback voltage VFB will droop. If VFB drops
below 0.3V the XRP7665 will detect a short-
circuit condition and reduce the switching
frequency to 90kHz for system protection. The
regulator will restart once the short-circuit has
been removed.
OVERVOLTAGE PROTECTION OVP
The XRP7665 has internal OVP. When VOUT
exceeds the OVP threshold (when VFB exceeds
1.1V) the power switching will be turned off.
The XRP7665 will restart when overvoltage
condition is removed.
PROGRAMMABLE SOFT-START
OVER-TEMPERATURE PROTECTION OTP
The soft-start time is fully programmable via
CSS capacitor, placed between the SS and
GND pin. The CSS is charged by a 6µA
constant-current source, generating a ramp
signal fed into non-inverting input of the error
amplifier. This ramp regulates the voltage on
comp pin during the regulator startup, thus
realizing soft-start. Calculate the required CSS
from:
If the junction temperature exceeds 160°C the
OTP circuit is triggered, turning off the internal
control circuit and switched M1 and M2. When
junction temperature drops below 140°C the
XRP7665 will restart.
APPLICATION INFORMATION
6μ
=
×
SETTING THE OUTPUT VOLTAGE
Where:
Use an external resistor divider to set the
output voltage. Program the output voltage
from:
tss is the required soft-start time
VFB is the feedback voltage (0.925V nominal)
1 = 2 ×
− 1
0.9 2 5
ENABLE FUNCTION
Where:
R1 is the resistor between VOUT and FB
The XRP7665 is enabled by raising the voltage
on the EN pin above 2.5V nominally. Connect
the EN pin to the VIN via a 1 0 0 k Ω r e s i s t o r
f o r
R2 is the resistor between FB and GND
automatic start-up. Shutdown is achieved by
pulling the EN pin voltage below 1.1V
nominally.
( n o mi n a l l y 1 0 k Ω)
0.925V is the nominal feedback voltage.
7/12 Rev. 2.0.1
© 2013 Exar Corporation
XRP7665
3A 18V Synchronous Step-Down Converter
of thumb, should be at least twice the output
voltage. When calculating the required
OUTPUT INDUCTOR
Select the output inductor for inductance L, DC
current rating IDC and saturation current rating
ISAT. IDC should be larger than regulator output
current. ISAT, as a rule of thumb, should be
50% higher than the regulator output current.
Since the regulator is rated at 3A then IDC≥3A
and ISAT≥4.5A. Calculate the inductance from:
capacitance,
usually
the
overriding
requirement is current load-step transient. If
the unloading transient (i.e., when load
transitions from a high to a low current) is
met, then usually the loading transient (when
load transitions from a low to a high current)
is met as well. Therefore calculate the COUT
based on the unloading transient requirement
from:
(
)
=
−
×
×
−
Where:
=
×
(
)
−
+
Δ I is peak-to-peak inductor current ripple
L
nominally set to 30%-40% of IOUT
Where:
fS is nominal switching frequency (340kHz)
L is the inductance calculated in the preceding
step
As an example, inductor values for several
common output voltages are shown in tables 1
and 2. Note that example inductors shown in
tables 1 and 2 are Wurth shielded inductors. If
the target application is not sensitive to EMI
then unshielded inductors may be used.
IHigh is the value of load-step prior to
unloading. This is nominally set equal to
regulator current rating (3A).
ILow is the value of load-step after unloading.
This is nominally set equal to 50% of regulator
current rating (1.5A).
Inductor
Example
Vtransient is the maximum permissible voltage
transient corresponding to the load step
mentioned above. Vtransient is typically specified
VOUT(V) ΔIL(p-p)(A)
L(µH)
744314101
744314101
744314101
744314760
744314760
744314490
0.9
0.7
0.6
0.6
0.5
0.6
10
10
10
7.6
7.6
4.9
5.0
3.3
2.5
1.8
1.5
1.2
from 3% to 5% of VOUT
.
ESR of the capacitor has to be selected such
that the output voltage ripple requirement
Δ V , nominally 1% of VOUT, is met. Voltage
OUT
ripple Δ V
is mainly composed of two
Table 1: Suggested inductor values for VIN=12V and
IOUT=3A
OUT
components: the resistive ripple due to ESR
and capacitive ripple due to COUT charge
transfer. For applications requiring low voltage
ripple, ceramic capacitors are recommended
because of their low ESR which is typically in
Inductor
VOUT(V) ΔIL(p-p)(A)
L(µH)
Example
744314490
744314490
744314490
744314490
744314490
0.7
0.8
0.7
0.6
0.5
4.9
4.9
4.9
4.9
4.9
3.3
2.5
1.8
1.5
1.2
the range of 5 mΩ. Therefore Δ V
capacitive. For ceramic capacitors calculate
is mainly
OUT
the Δ V from:
OUT
=
8 ×
×
Table 2: Suggested inductor values for VIN=5V and
IOUT=3A
Where:
Δ I is from table 1 or 2
L
COUT is the value calculated above
OUTPUT CAPACITOR COUT
fs is nominal switching frequency (340kHz)
Select the output capacitor for voltage rating,
capacitance COUT and Equivalent Series
Resistance ESR. The voltage rating, as a rule
© 2013 Exar Corporation
8/12
Rev. 2.0.1
XRP7665
3A 18V Synchronous Step-Down Converter
If tantalum or electrolytic capacitors are used
t h e nVOUTΔis essentially a function of ESR:
Circuit configuration is shown in figures 16 and
17. The external bootstrap diode is also
recommended where duty cycle (VOUT/VIN) is
larger than 65%.
=
×
INPUT CAPACITOR CIN
Select the input capacitor for voltage rating,
RMS current rating and capacitance. The
voltage rating should be at least 50% higher
than the regulator’ smaximum input voltage.
C a l c u l a t e t h e c a p a c i t o r ’ s c u r r e n t
1N4148
VIN = 5V
IN
BS
r m:
10nF
XRP7665
( )
× 1 −
=
×
,
Where:
IOUT i s r e g u l a t o r ’ s ma3xAi) mu m c u r r e n t
SW
(
Fig. 16: Optional external bootstrap diode
where input voltage is fixed at 5V
D is duty cycle (D=VOUT/VIN)
Calculate the CIN capacitance from:
(
)
×
×
−
1N4148
BS
=
×
×
Where:
10nF
XRP7665
VOUT = 5V
or 3.3V
Δ V is the permissible input voltage ripple,
IN
SW
nominally set at 1% of VIN
COUT
OPTIONAL SCHOTTKY DIODE
An optional Schottky diode may be paralleled
between the GND pin and SW pin to improve
the regulator efficiency. Examples are shown
in Table 3.
Fig. 17: Optional external bootstrap diode
where output voltage is 5V or 3.3V
LOOP COMPENSATION
XRP7665 utilizes current-mode control. This
allows using minimum of external
a
Voltage/Current
components to compensate the regulator. In
general only two components are needed: RC
and CC. Proper compensation of the regulator
(determining RC and CC) results in optimum
transient response. In terms of power supply
control theory, the goals of compensation are
to choose RC and CC such that the regulator
loop gain has a crossover frequency fc
between 15kHz and 34kHz. The corresponding
phase-margin should be between 45 degrees
and 65 degrees. An important characteristic of
current-mode buck regulator is its dominant
pole. The frequency of the dominant pole is
given by:
Part Number
Vendor
Rating
Diodes, Inc.
Diodes, Inc.
30V/1A
30V/1A
B130
SK13
International
Rectifier
30V/1A
MBRS130
Table 3. Optional Schottky diode
EXTERNAL BOOTSTRAP DIODE
A low-cost diode, such as 1N4148, is
recommended for higher efficiency when the
input voltage is 5V or the output is 5V or 3.3V.
© 2013 Exar Corporation
9/12
Rev. 2.0.1
XRP7665
3A 18V Synchronous Step-Down Converter
1
XRP7665’ s
constitute a zero. The frequency of this
E r r o r
A mp l i f i e r
a n d
=
2 ×
×
compensating zero is given by:
1
=
where Rload is the output load resistance.
2 ×
×
The uncompensated regulator has a constant
gain up to its pole frequency, beyond which
the gain decreases at -20dB/decade. The zero
arising from the output capacitor’s ESR is
inconsequential if ceramic COUT is used. This
simplifies the compensation. The RC and CC,
which are placed between the output of
For the typical application circuit, RC=6.8k Ω
and CC=3.9nF provide a satisfactory
compensation. Please contact EXAR if you
need assistance with the compensation of your
particular circuit.
TYPICAL APPLICATIONS
Fig. 18: XRP7665 Typical Application Diagram - 12V to 3.3V Conversion
© 2013 Exar Corporation
10/12
Rev. 2.0.1
XRP7665
3A 18V Synchronous Step-Down Converter
PACKAGE SPECIFICATION
8-PIN SOIC EXPOSED PAD
Unit: mm (inch)
Eject hole, oriented hole and mold mark are optional.
© 2013 Exar Corporation
11/12
Rev. 2.0.1
XRP7665
3A 18V Synchronous Step-Down Converter
REVISION HISTORY
Revision
Date
Description
02/14/2011
10/13/2011
Initial release of datasheet
1.0.0
1.1.0
Added Moisture Sensitivity Level (MSL) information
Reformat of datasheet
Changed min operating input voltage from 4.75V to 4.5V
Updated Electrical Specifications parameter (quiescent current, feedback voltage, high
and low side switch on-resistance, oscillator frequency, EN shutdown threshold voltage
and hysteresis, EN lockout threshold voltage and hysteresis, UVLO threshold and
hysteresis, soft-start time)
Updated figure 2: XRP7665 block diagram
Updated Pin Description, EN pin description
02/12/2013
3/29/2013
2.0.0
2.0.1
Updated all Typical Performance Characteristics curves
Updated Enable pin description
Deleted Electrical Specification parameters (shutdown supply current, EN shutdown
threshold voltage and hysteresis, EN lockout threshold voltage and hysteresis)
Added Electrical Specification parameters (EN enable threshold voltage and hysteresis)
A d d e d “ E N A B L E FpaUrNagCraTphI tOoNth”e theory of operation section.
FOR FURTHER ASSISTANCE
Email:
customersupport@exar.com
powertechsupport@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
u s e r ’ s
s p e c i f i c
a p p l i c a t i o n .
Wh i l e t h e i n f o r cmhaectkeid;o nno reispnonstibhiliity,s howpeuvebr,l i c a t i o n
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.
© 2013 Exar Corporation
12/12
Rev. 2.0.1
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