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PDF XRP6141 Data sheet ( Hoja de datos )
| Número de pieza | XRP6141 | |
| Descripción | 35A Synchronous Step Down COT Controller | |
| Fabricantes | Exar | |
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XRP6141
35A Synchronous Step Down COT Controller
July 2015
GENERAL DESCRIPTION
The XRP6141 is a synchronous step-down
controller for point-of load supplies up to 35A.
A wide 4.5V to 22V input voltage range allows
for single supply operation from industry
standard 5V, 12V and 19.6V rails.
With a proprietary emulated current mode
Constant On-Time (COT) control scheme, the
XRP6141 provides extremely fast line and load
transient response using ceramic output
capacitors. It requires no loop compensation
hence simplifying circuit implementation and
reducing overall component count. The control
loop also provides exceptional line regulation
and maintains constant operating frequency. A
selectable power saving mode, allows the user
to operate in discontinuous mode (DCM) at light
current loads thereby significantly increasing
the converter efficiency.
A host of protection features, including over-
current, over-temperature, short-circuit and
UVLO, help achieve safe operation under
abnormal operating conditions.
The XRP6141 is available in RoHS compliant,
green/halogen free space-saving 16-pin 3x3
QFN package.
Rev. 2.0.0
APPLICATIONS
Networking and Communications
Fast Transient Point-of-Loads
Industrial and Medical Equipment
Embedded High Power FPGA
FEATURES
35A Capable Step Down Controller
Wide Input Voltage Range
o 5V to 22V Single Supply
o 4.5V to 5.5V Low VIN
Integrated high Current 2A/3A Drivers
0.6V to 18V Adjustable Output Voltage
Proprietary Constant On-Time Control
No Loop Compensation Required
Ceramic Output Cap. Stable operation
Programmable 200ns-2µs
Constant 200kHz-800kHz Frequency
Selectable CCM or CCM/DCM Operation
Programmable hiccup current limit
with thermal compensation
Precision Enable and Power-Good Flag
Programmable Soft-start
Integrated Bootstrap diode
16-pin QFN Package
TYPICAL APPLICATION DIAGRAM
Fig. 1: XRP6141 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  
XRP6141
35A Synchronous Step Down COT Controller
PIN DESCRIPTION
Name
GL
NC
SW
GH
BST
ILIM
EN/MODE
TON
SS
PGOOD
FB
AGND
VIN
VCC
PGND
Exposed Pad
Pin Number
1
2
3
4
5
6
7
8
9
10
11
12, 13
14
15
16
Description
Driver output for Low-side N-channel synchronous MOSFET.
Internally not connected. Leave this pin floating.
Lower supply rail for high-side gate driver GH. Connect this pin to the junction between
the two external N-channel MOSFETs.
Driver output for high-side N-channel switching MOSFET.
High-side driver supply pin. Connect a 0.1uF bootstrap capacitor between BST and SW.
Over-current protection programming. Connect with a resistor to the Drain of the low-
side MOSFET.
Precision enable pin. Pulling this pin above 1.9V will turn the IC on and it will operate in
Forced CCM. If the voltage is raised above 3.0V then the IC will operate in DCM or CCM
depending on load.
Constant on-time programming pin. Connect with a resistor to AGND.
Soft-Start pin. Connect an external capacitor between SS and AGND to program the
soft-start rate based on the 10uA internal source current.
Power-good output. This open-drain output is pulled low when VOUT is outside the
regulation.
Feedback input to feedback comparator. Connect with a set of resistors to VOUT and
GND in order to program VOUT.
Analog ground. Control circuitry of the IC is referenced to this pin.
IC supply input. Provides power to internal LDO.
The output of LDO. For operation using a 5V rail, VCC should be shorted to VIN.
Low side driver ground
Thermal pad for heat dissipation. Connect to AGND with a short trace.
ORDERING INFORMATION
Part Number
Temperature
Range
Marking
XRP6141EL-F
XRP6141ELMTR-F
XRP6141ELTR-F
XRP6141EVB
-40°C≤TJ≤+125°C
6141
-40°C≤TJ≤+125°C
YWW
-40°C≤TJ≤+125°C
XXXX
XRP6141 Evaluation Board
Package
3x3mm
QFN16
Packing
Quantity
Note 1
Tray
250/Tape & Reel
Lead Free and/or
Halogen Free
3k/Tape & Reel
“Y” = Year – “WW” = Work Week – “X” = Lot Number; when applicable.
© 2015 Exar Corporation
5/14
Rev. 2.0.0
5 Page 
XRP6141
35A Synchronous Step Down COT Controller
Note that switching frequency f will increase somewhat, as
a function of increasing load current and increasing losses
(see figure 22).
OVER-CURRENT PROTECTION (OCP)
If load current exceeds the programmed over-current IOCP
for four consecutive switching cycles, then IC enters hiccup
mode of operation. In hiccup the MOSFET gates are turned
off for 110ms (hiccup timeout). Following the hiccup
timeout a soft-start is attempted. If OCP persists, hiccup
timeout will repeat. The IC will remain in hiccup mode until
load current is reduced below the programmed IOCP. In
order to program over-current protection use the following
equation:
������������������������
=
(������������������������
× ������������������)
������������������������
+
8������������
Where:
RLIM is resistor value for programming IOCP
IOCP is the over-current value to be programmed
RDS is the MOSFET rated on resistance
8mV is the OCP comparator offset
ILIM is the internal current that generates the necessary
OCP comparator threshold (use 45uA)
Note that ILIM has a positive temperature coefficient of
0.4%/°C. This is meant to roughly match and compensate
for positive temperature coefficient of the synchronous
FET. In order for this feature to be effective the
temperature rise of the IC should approximately match the
temperature rise of the FET.
SHORT-CIRCUIT PROTECTION (SCP)
If the output voltage drops below 60% of its programmed
value, the IC will enter hiccup mode. Hiccup will persist
until short-circuit is removed. SCP circuit becomes active
after PGOOD asserts high.
OVER-TEMPERATURE PROTECTION (OTP)
OTP triggers at a nominal die temperature of 150°C. The
gate of switching FET and synchronous FET are turned off.
When die temperature cools down to 135°C, soft-start is
initiated and operation resumes.
PROGRAMMING THE OUTPUT VOLTAGE
Use an external voltage divider as shown in figure 1 to
program the output voltage VOUT.
������1 = ������2 × (���������0���.���6��������� − 1)
R2 recommended range is 2kΩ to 10kΩ.
PROGRAMMING THE SOFT-START
Place a capacitor CSS between the SS and GND pins to
program the soft-start. In order to program a soft-start
time of TSS, calculate the required capacitance CSS from
the following equation:
������������������
=
������������������
×
10������������
0.6������
FEED-FORWARD CAPACITOR (CFF)
A feed-forward capacitor (CFF) may be necessary
depending on the Equivalent Series Resistance (ESR) of
COUT. If only ceramic output capacitors are used then a CFF
is necessary. Calculate CFF from:
������������������
=
2
×
������
×
1
������1 ×
7 × ������������������
where:
R1 is the resistor that CFF is placed in parallel with
fLC is the frequency of the output filer double pole
fLC must be less than 15kHz when using ceramic COUT. If
necessary, increase COUT and/or L in order to meet this
constraint.
When using capacitors with higher ESR such as Panasonic
TPE series, a CFF is not required provided following
conditions are met:
1. The frequency of the output LC double pole fLC
should be less than 10kHz.
2. The frequency of ESR zero fZERO,ESR should be at
least five times larger than fLC.
Note that if fZERO,ESR is less than 5 x fLC, then it is
recommended to set the fLC at less than 2kHz. CFF is still
not required.
FEED-FORWARD RESISTOR (RFF)
Poor PCB layout and/or extremely fast switching FETs can
cause switching noise at the output and may couple to the
FB pin via CFF. Excessive noise at FB will cause poor load
regulation. To solve this problem place a resistor RFF in
series with CFF. RFF value up to 2% of R1 is acceptable.
MAXIMUM ALLOWABLE VOLTAGE RIPPLE AT
FB PIN
Note that the steady-state voltage ripple at feedback pin
(VFB,RIPPLE) must not exceed 50mV in order for the controller
to function correctly. If VFB,RIPPLE is larger than 50mV then
COUT should be increased as necessary in order to keep the
VFB,RIPPLE below 50mV.
© 2015 Exar Corporation
11/14
Rev. 2.0.0
11 Page | ||
| Páginas | Total 14 Páginas | |
| PDF Descargar | [ Datasheet XRP6141.PDF ] | |
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