© 2014 Exar Corporation
XR79115
22V, 15A Synchronous Step Down COT Power Module
exar.com/XR79115
Rev 1B
1 / 19
General Description
The XR79115 is a 15A synchronous step-down Power Module for point-of
load supplies. A wide 5V to 22V input voltage range allows for single sup-
ply operation from industry standard 5V, 12V, and 19.6V rails.
With a proprietary emulated current mode Constant On-Time (COT) con-
trol scheme, the XR79115 provides extremely fast line and load transient
response using ceramic output capacitors. It requires no loop compensa-
tion hence simplifying circuit implementation and reducing overall compo-
nent count. The control loop also provides 0.35% load and 0.1% 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. With a 96% peak efficiency and 90% for loads as low as
100mA, the XR79115 is suitable for applications where low power losses
are important.
A host of protection features, including over-current, over-temperature,
short-circuit and UVLO, help achieve safe operation under abnormal
operating conditions.
The XR79115 is available in a RoHS compliant, green/halogen free
space-saving 68-pin 12x12x4mm QFN package. With integrated control-
ler, drivers, bootstrap diode and capacitor, MOSFETs, inductor, CIN and
COUT, this solution allows the smallest possible 15A POL design.
FEATURES
Controller, drivers, bootstrap diode and capaci-
tor, MOSFETs, Inductor, CIN and COUT integrated
in one package
15A Step Down Module
Wide 5V to 22V Input Voltage Range
>0.6V Adjustable Output Voltage
Proprietary Constant On-Time Control
No Loop Compensation Required
Stable Ceramic Output Capacitor Operation
Programmable 200ns to 2μs On-Time
Constant 400kHz to 600kHz Frequency
Selectable CCM or CCM/DCM
CCM/DCM for high efficiency at light-load
CCM for constant frequency at light-load
Programmable Hiccup Current Limit with Ther-
mal Compensation
Precision Enable and Power Good flag
Programmable Soft-start
68-pin 12x12x4mm QFN package
APPLICATIONS
Networking and Communications
Fast Transient Point-of-Loads
Industrial and Medical Equipment
Embedded High Power FPGA
Ordering Information – back page
Typical Application
1.180
1.185
1.190
1.195
1.200
1.205
1.210
1.215
1.220
4 6 8 10 12 14 16 18 20 22
V
OUT
(V)
V
IN
(V)
PGND
FB
ILIM
SW
XR79115
VIN
EN/MODE
PGOOD
VCC
SS
TON
AGND
CSS RON
CVCC
Enable/Mode
Power Good
R3
VIN
VOUT
RLIM R1
R2
COUT
CIN
PVIN
VOUT
Line Regulation
© 2014 Exar Corporation
XR79115
2 / 19 exar.com/XR79115
Rev 1B
Absolute Maximum Ratings
Stresses beyond the limits listed below may cause perma-
nent damage to the device. Exposure to any Absolute Max-
imum Rating condition for extended periods may affect
device reliability and lifetime.
PVIN, VIN...................................................................-0.3V to 25V
VCC...........................................................................-0.3V to 6.0V
BST..........................................................................-0.3V to 31V1
BST-SW.......................................................................-0.3V to 6V
SW, ILIM...................................................................-1V to 25V1, 2
ALL other pins.................................................-0.3V to VCC+0.3V
Storage Temperature...........................................-65°C to +150°C
Junction Temperature..........................................................150°C
Power Dissipation...............................................Internally Limited
Lead Temperature (Soldering, 10 sec)......................260°C MSL3
ESD Rating (HBM - Human Body Model)...............................2kV
Operating Conditions
PVIN...............................................................................3V to 22V
VIN..............................................................................4.5V to 22V
VCC............................................................................4.5V to 5.5V
SW, ILIM.....................................................................-1V to 22V1
PGOOD, VCC, TON, SS, EN, FB...............................-0.3V to 5.5V
Switching Frequency......................................400kHz to 600kHz3
Junction Temperature Range..............................-40°C to +125°C
JEDEC51 Package Thermal Resistance, JA................15.4°C/W
Package Power Dissipation at 25°C.......................................6.5W
Note 1: No external voltage applied.
Note 2: SW pin’s minimum DC range is -1V, transient is -5V for less than
50ns.
Note 3: Recommended frequency for optimum performance
Electrical Characteristics
Unless otherwise noted: TJ= 25°C, VIN=12V, BST=VCC, SW=AGND=PGND=0V, CVCC=4.7uF. Limits applying over the full
operating temperature range are denoted by a “•”
Symbol Parameter Conditions Min Typ Max Units
Power Supply Characteristics
VIN Input Voltage Range
VCC regulating 522
V
VCC tied to VIN 4.5 5.5
IVIN VIN Input Supply Current Not switching, VIN = 12V, VFB = 0.7V 0.7 2 mA
IVCC VCC Quiescent Current Not switching, VCC=VIN = 5V, VFB = 0.7V 0.7 2 mA
IVIN VIN Input Supply Current f=500kHz, RON=61.9k, VFB=0.58V 17 mA
IOFF Shutdown Current Enable = 0V, VIN = 12V 1 µA
Enable and Under-Voltage Lock-Out UVLO
VIH_EN EN Pin Rising Threshold 1. 8 1. 9 2 . 0 V
VEN_HYS EN Pin Hysteresis 50 mV
VIH_EN EN Pin Rising Threshold for DCM/
CCM operation
2.8 3.0 3.1 V
VEN_HYS EN Pin Hysteresis 100 mV
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XR79115
3 / 19 exar.com/XR79115
Rev 1B
VCC UVLO Start Threshold, Rising
Edge
4.00 4.25 4.40 V
VCC UVLO Hysteresis 200 mV
Reference Voltage
VREF Reference Voltage
VIN = 5V to 22V, VCC regulating 0.597 0.600 0.603 V
VIN = 4.5V to 5.5V, VCC tied to VIN 0.596 0.600 0.604 V
VIN = 5V to 22V, VCC regulating
0.594 0.600 0.606 V
VIN = 4.5V to 5.5V, VCC tied to VIN
DC Line Regulation CCM, closed loop, VIN=4.5V-22V, applies
to any COUT
±0.10 %
DC Load Regulation CCM, closed loop, IOUT=0A-15A, applies
to any COUT
±0.35 %
Programmable Constant On-Time
TON(MIN) Minimum Programmable On-Time RON = 6.98k, VIN = 22V 120 ns
TON2 On-Time 2 RON = 6.98k, VIN = 12V 156 192 228 ns
f Corresponding to On-Time 2 VOUT = 1.0V 450 535 660 kHz
TON3 On-Time 3 RON = 16.2k, VIN = 12V 341 412 483 ns
Minimum Off-Time 250 350 ns
Diode Emulation Mode
Zero Crossing Threshold DC value measured during test -2 mV
Soft-start
SS Charge Current -14 -10 -6 µA
SS Discharge Current Fault present 1mA
VCC Linear Regulator
VCC Output Voltage
VIN = 6V to 22V, ILOAD = 0 to 30mA 4.8 5.0 5.2 V
VIN = 5V, ILOAD = 0 to 20mA 4.6 4.8 V
Power Good Output
Power Good Threshold -10 -7.5 -5 %
Power Good Hysteresis 24 %
Power Good Sink Current 1 mA
Protection: OCP, OTP, Short-Circuit
Hiccup Timeout 110 m s
ILIM Pin Source Current 45 50 55 µA
ILIM Current Temperature Coefficient 0.4 %/°C
OCP Comparator Offset -8 0 +8 mV
Symbol Parameter Conditions Min Typ Max Units
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XR79115
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Rev 1B
Note 1: Guaranteed by design
Current Limit Blanking GL rising>1V 100 ns
Thermal Shutdown Threshold1Rising temperature 150 °C
Thermal Hysteresis115 °C
VSCTH Feedback Pin Short-Circuit
Threshold
Percent of VREF
, short circuit is active after
PGOOD is asserted
50 60 70 %
Output Power Stage
RDSON
High-Side MOSFET RDSON
IDS = 2A, VGS=4.5V
8.3 10 m
Low-Side MOSFET RDSON 4.2 5 m
IOUT Maximum Output Current 15 A
L Output Inductance 0.45 0.56 0.67 uH
CIN Input Capacitance 1uF
COUT Output Capacitance 2.2 uF
CBST Bootstrap Capacitance 0.1 uF
Symbol Parameter Conditions Min Typ Max Units
© 2014 Exar Corporation
XR79115
5 / 19 exar.com/XR79115
Rev 1B
Pin Configuration, Top View
© 2014 Exar Corporation
XR79115
6 / 19 exar.com/XR79115
Rev 1B
Pin Assignments
Type: A = Analog, I = Input, O = Output, I/O = Input/Output, PWR = Power, OD = Open-Drain
Pin No. Pin Name Type Description
1 SS A Soft-start pin. Connect an external capacitor between SS and AGND to program the soft-start
rate based on the 10uA internal source current.
2 PGOOD OD, O Power-good output. This open-drain output is pulled low when VOUT is outside the regulation.
3 FB A Feedback input to feedback comparator. Connect with a set of resistors to VOUT and AGND in
order to program VOUT.
4, 67, AGND
Pad
AGND A Analog ground. Control circuitry of the IC is referenced to this pin.
5 VIN PWR IC supply input. Provides power to internal LDO.
6 VCC PWR The output of LDO. Bypass with a 4.7uF capacitor to AGND. For operation from a 5VIN rail,
VCC should be tied to VIN.
7, GL pad GL O Driver output for Low-side N-channel synchronous MOSFET. It is internally connected to the
gate of the FET. Leave this pin floating.
8 PGND PWR Controller low-side driver ground. Connect with a short trace to closest PGND pins or PGND
pad.
13-23, 54,
55, PGND
pads
PGND PWR Ground of the power stage. Should be connected to the system’s power ground plane.
9-12, 24-29,
SW Pad
SW PWR Switching node. It is internally connected. Use thermal vias and/or sufficient PCB land area in
order to heatsink the low-side FET and the inductor.
30-53,
VOUT pads
VOUT PWR Output of the power stage. Place the output filter capacitors as close as possible to these pins.
56-62, PVIN
Pad
PVIN PWR Power stage input voltage. Place the input filter capacitors as close as possible to these pins.
63, 64, BST
Pad
BST A Controller high-side driver supply pin. It is internally connected to SW via a 0.1uF bootstrap
capacitor. Leave these pins floating.
65 ILIM A Over-current protection programming. Connect with a short trace to SW pins.
66 EN/MODE I 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.
68 TON A Constant on-time programming pin. Connect with a resistor to AGND.
© 2014 Exar Corporation
XR79115
7 / 19 exar.com/XR79115
Rev 1B
Functional Block Diagram
Q
Q
R
S
Dead
Time
Control
On-Time
1.9 V
Hiccup
Mode
+-
PGND
FB
VIN
GH
Minimum
On Time
Enable
Hiccup
OCP
comparator
Feedback
comparator
ESR
emulation &
DC correction
PGOOD
LDO
VCC
VCC
GL
VOUT
BST
VCC
50uA
+
-
+
-
+
-
3 V
-2 mV
SW
Enable LDO
CCM or CCM/DCM
Zero Cross Detect
If 8 consecutive ZCD
Then DCM
If 1 non-ZCD
Then exit DCM
Q
Q
R
S
AGND ILIM
If four
consecutive OCP
VIN
TON
+
-
+
-
+
-
PGOOD comparator
Short-circuit detection
0.555 V
0.36 V
Switching
Enabled
10uA
+
-
Switching
Enabled
SS
0.6 V
+
-
+
-
Switching
Enabled
Enable LDO VCC UVLO
4.25 V
OTP
150 C
TJ
VCC
TON
Enable LDO
PVIN
L
CBST
0.1uF
PGND
CIN
1uF
PGND
COUT
2.2uF
SW
FB 0.6V
EN/
MODE
GL
GL
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XR79115
8 / 19 exar.com/XR79115
Rev 1B
Typical Performance Characteristics
Unless otherwise noted: VIN = 12V, VOUT=1.2V, IOUT=15A, f=500kHz, TA = 25°C. Schematic from the application information
section.
Figure 1: Load Regulation Figure 2: Line regulation
Figure 3: TON versus RON Figure 4: TON versus VIN, RON=6.98k
Figure 5: frequency versus IOUT Figure 6: frequency versus VIN
1.180
1.185
1.190
1.195
1.200
1.205
1.210
1.215
1.220
4 6 8 10121416182022
V
OUT
(V)
V
IN
(V)
1.180
1.185
1.190
1.195
1.200
1.205
1.210
1.215
1.220
0 2 4 6 8 10 12 14 16
V
OUT
(V)
I
OUT
(A)
100
200
300
400
500
0 5 10 15 20
T
ON
(ns)
R
ON
(kΩ)
Calculated
Typical
100
200
300
400
500
4 6 8 10 12 14 16 18 20 22
T
ON
(ns)
V
IN
(V)
Calculated
Typical
0
100
200
300
400
500
600
0 5 10 15
f (kHz)
I
OUT
(A)
0
100
200
300
400
500
600
4 6 8 10 12 14 16 18 20 22
f (kHz)
V
IN
(V)
© 2014 Exar Corporation
XR79115
9 / 19 exar.com/XR79115
Rev 1B
Typical Performance Characteristics
Unless otherwise noted: VIN = 12V, VOUT=1.2V, IOUT=15A, f=500kHz, TA = 25°C. Schematic from the application information
section.
Figure 7: IOCP versus RLIM Figure 8: VREF versus temperature
Figure 9: ILIM versus temperature Figure 10: TON versus temperature, RON=16.2k
Figure 11: Inductance versus Current Figure 12: Maximum recommended VOUT versus f, VIN=12V
0
5
10
15
20
25
30
1.50 1.75 2.00 2.25 2.50
I
OCP
(A)
R
LIM
(kΩ)
590
595
600
605
610
-40 -20 0 20 40 60 80 100 120
V
REF
(mV)
T
J
(°C)
0.00
0.10
0.20
0.30
0.40
0.50
0.60
0.70
0.80
0 5 10 15 20 25 30 35
Inductance (uH)
Current (A)
0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
400 500 600
V
OUT
(V)
frequency (kHz)
350
360
370
380
390
400
410
420
430
440
450
-40-200 20406080100120
TON (ns)
T
J
(°C)
30
40
50
60
70
-40 -20 0 20 40 60 80 100 120
ILIM (uA)
T
J
(°C)
© 2014 Exar Corporation
XR79115
10 / 19 exar.com/XR79115
Rev 1B
Typical Performance Characteristics
Unless otherwise noted: VIN = 12V, VOUT=1.2V, IOUT=15A, f=500kHz, TA = 25°C. Schematic from the application information
section.
Figure 13: Steady state, CCM, IOUT=15A Figure 14: Steady state, DCM, IOUT=0A
Figure 15: Power up, Forced CCM Figure 16: Power up, DCM/CCM
Figure 17: Load step, Forced CCM, 0A-7.5A-0A Figure 18: Load step, DCM/CCM, 0A-7.5A-0A
© 2014 Exar Corporation
XR79115
11 / 19 exar.com/XR79115
Rev 1B
Efficiency and Package Thermal Derating
Unless otherwise noted: TAMBIENT = 25°C, No Air flow, f=500kHz, Schematic from the application information section.
Figure 19: Efficiency, VIN=5V Figure 20: Maximum TAMBIENT vs IOUT, VIN=5V
Figure 21: Efficiency, VIN=12V Figure 22: Maximum TAMBIENT vs IOUT, VIN=12V
Figure 23: Efficiency, VIN=19.6V Figure 24: Maximum TAMBIENT vs IOUT, VIN=19.6V
60
62
64
66
68
70
72
74
76
78
80
82
84
86
88
90
0.1 1.0 10.0
Efficiency %
I
OUT
(A)
1.8V DCM 1.8V CCM
1.2V DCM 1.2V CCM
30
40
50
60
70
80
90
100
110
120
130
123456789101112131415
TAMBIENT(°C)
IOUT (A)
1.2 VOUT
1.8 VOUT
30
40
50
60
70
80
90
100
110
120
130
123456789101112131415
T
AMBIENT
(°C)
I
OUT
(A)
1.0 VOUT
1.8 VOUT
3.3 VOUT
70
72
74
76
78
80
82
84
86
88
90
92
94
96
98
100
0.1 1.0 10.0
Efficiency %
I
OUT
(A)
3.3V DCM 3.3V CCM
2.5V DCM 2.5V CCM
1.8V DCM 1.8V CCM
1.5V DCM 1.5V CCM
1.2V DCM 1.2V CCM
1.0V DCM 1.0V CCM
600kHz
70
72
74
76
78
80
82
84
86
88
90
92
94
96
98
100
0.1 1.0 10.0
Efficiency %
I
OUT
(A)
3.3V DCM 3.3V CCM
2.5V DCM 2.5V CCM
1.8V DCM 1.8V CCM
1.5V DCM 1.5V CCM
1.2V DCM 1.2V CCM
1.0V DCM 1.0V CCM
30
40
50
60
70
80
90
100
110
120
130
123456789101112131415
T
AMBIENT
(°C)
I
OUT
(A)
1.0 VOUT
1.8 VOUT
3.3 VOUT
© 2014 Exar Corporation
XR79115
12 / 19 exar.com/XR79115
Rev 1B
Functional Description
XR79115 is a synchronous step-down proprietary emulated
current-mode Constant On-Time (COT) Module. The on-
time, which is programmed via RON, is inversely propor-
tional to VIN and maintains a nearly constant frequency.
The emulated current-mode control is stable with ceramic
output capacitors.
Each switching cycle begins with GH signal turning on the
high-side (switching) FET for a preprogrammed time. At the
end of the on-time, the high-side FET is turned off and the
low-side (synchronous) FET is turned on for a preset mini-
mum time (250ns nominal). This parameter is termed Mini-
mum Off-Time. After the minimum off-time, the voltage at
the feedback pin FB is compared to an internal voltage
ramp at the feedback comparator. When VFB drops below
the ramp voltage, the high-side FET is turned on and the
cycle repeats. This voltage ramp constitutes an emulated
current ramp and makes possible the use of ceramic
capacitors, in addition to other capacitor types, for output fil-
tering.
Enable/Mode Input (EN/MODE)
EN/MODE pin accepts a tri-level signal that is used to con-
trol turn on/off. It also selects between two modes of opera-
tion: ‘Forced CCM’ and ‘DCM/CCM’. If EN is pulled below
1.8V, the Module shuts down. A voltage between 2.0V and
2.8V selects the Forced CCM mode which will run the Mod-
ule in continuous conduction at all times. A voltage higher
than 3.1V selects the DCM/CCM mode which will run the
Module in discontinuous conduction at light loads.
Selecting the Forced CCM Mode
In order to set the Module to operate in Forced CCM, a volt-
age between 2.0V and 2.8V must be applied to EN/MODE.
This can be achieved with an external control signal that
meets the above voltage requirement. Where an external
control is not available, the EN/MODE can be derived from
VIN. If VIN is well regulated, use a resistor divider and set
the voltage to 2.5V. If VIN varies over a wide range, the cir-
cuit shown in figure 25 can be used to generate the
required voltage. Note that at VIN of 5V and 22V the nomi-
nal Zever voltage is 3.8V and 4.7V respectively. Therefore
for VIN in the range of 5V to 22V, the circuit shown in figure
25 will generate VEN required for Forced CCM.
Selecting the DCM/CCM Mode
In order to set the Module operation to DCM/CCM, a volt-
age between 3.1V and 5.5V must be applied to EN/MODE
pin. If an external control signal is available, it can be
directly connected to EN/MODE. In applications where an
external control is not available, EN/MODE input can be
derived from VIN. If VIN is well regulated, use a resistor
divider and set the voltage to 4V. If VIN varies over a wide
range, the circuit shown in figure 26 can be used to gener-
ate the required voltage.
Figure 25: Selecting Forced CCM by deriving EN/MODE from
VIN
Figure 26: Selecting DCM/CCM by deriving EN/MODE from
VIN
R1
30.1k, 1%
RZ
10k
EN/MODE
R2
35.7k, 1%
Zener
MMSZ4685T1G or Equivalent
IN
V
Zener
MM SZ4685T1G or Equivalent
RZ
10k
EN/MODE
VIN
VEN
© 2014 Exar Corporation
XR79115
13 / 19 exar.com/XR79115
Rev 1B
Programming the On-Time
The On-Time TON is programmed via resistor RON accord-
ing to following equation:
where TON is calculated from:
where:
f is the desired switching frequency at nominal IOUT
Eff is the Module efficiency corresponding to nominal IOUT
shown in figures 19, 21, 23
Substituting for TON in the first equation we get:
Over-Current Protection (OCP)
If load current exceeds the programmed over-current, IOCP
,
for four consecutive switching cycles, then Module enters
hiccup mode of operation. In hiccup, the MOSFET gates
are turned off for 110ms (hiccup timeout). Following the hic-
cup timeout, a soft-start is attempted. If OCP persists, hic-
cup timeout will repeat. The Module will remain in hiccup
mode until load current is reduced below the programmed
IOCP . In order to program the over-current protection, use
the following equation:
Where:
RLIM is resistor value for programming IOCP
IOCP is the over-current threshold to be programmed
RDS is the MOSFET rated On Resistance (5m)
8mV is the OCP comparator maximum offset
ILIM is the internal current that generates the necessary
OCP comparator threshold (use 45A).
Note that ILIM has a positive temperature coefficient of
0.4%/°C (figure 9). This is meant to roughly match and
compensate for positive temperature coefficient of the syn-
chronous FET. Graph of typical IOCP versus RLIM is shown
in figure 7.
Short-Circuit Protection (SCP)
If the output voltage drops below 60% of its programmed
value, the Module will enter hiccup mode. Hiccup will per-
sist until short-circuit is removed. SCP circuit becomes
active after PGOOD asserts high.
Over-Temperature (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 ini-
tiated and operation resumes.
Programming the Output Voltage
Use an external voltage divider as shown in the Application
Circuit to program the output voltage VOUT
.
where R2 has a nominal value of 2kΩ.
Programming the Soft-start
Place a capacitor CSS between the SS and AGND 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:
Feed-Forward Capacitor (CFF)
A feed-forward capacitor (CFF) may be necessary depend-
ing on the Equivalent Series Resistance (ESR) of COUT
. If
RON
VIN TON 25 9–
10–
2.85 10–
10
------------------------------------------------------------
=
TON
VOUT
VIN fEff
------------------------------
=
RON
VOUT
fEff
---------------
25 9–
10VIN
–
2.85 10–
10
-------------------------------------------------------------------------
=
RLIM IOCP RDS8mV+
ILIM
------------------------------------------------------
=
R1 R2 VOUT
0.6
------------- 1–
=
CSS TSS 10A
0.6V
--------------
=
© 2014 Exar Corporation
XR79115
14 / 19 exar.com/XR79115
Rev 1B
only ceramic output capacitors are used for COUT then a
CFF is necessary. Calculate CFF from:
where:
R1 is the resistor that CFF is placed in parallel with
80kHz is the location of the Zero formed by R1 and CFF
Note that minimum required COUT is 140uF when using
ceramic capacitors.
When using capacitors with higher ESR, such as PANA-
SONIC TPE series, a CFF is not required provided following
conditions are met:
1. The frequency of output filter LC double-pole fLC should
be less than 15kHz.
2. The frequency of ESR Zero fZero,ESR should be at least
three times larger than fLC.
As an example the application circuit has fLC=8.3kHz and
fZero,ESR=23.4kHz.
Note that the steady-state voltage ripple at feedback pin FB
(VFB,RIPPLE) must not exceed 50mV in order for Module 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.
Feed-Forward Resistor (RFF)
Poor PCB layout can cause FET switching noise at the out-
put 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.
CFF
1
280kHz R1
---------------------------------------------------
=
© 2014 Exar Corporation
XR79115
15 / 19 exar.com/XR79115
Rev 1B
Application Circuit
OPTIONAL
CVCC
4.7uF
VCC
R4 10k R3 38.3k
FB
U1
XR79115
SS
1
FB
3
PGOOD
2
AGND
4
SW
9
SW
10
SW
11
SW
12
VIN
5
VCC
6
GL
7
SW PAD
PGND
13
PGND
14
PGND
17
PGND
19
PGND
20
PGND
21
PGND
22
PGND
23
PGND PAD 1
PGND
18
PGND
8
PGND
16 PGND
15
SW
24
SW
25
SW
26
SW
27
SW
28
SW
29
VOUT 30
VOUT 31
VOUT 32
VOUT 33
VOUT 34
VOUT 35
VOUT 36
VOUT 37
VOUT 38
VOUT 39
VOUT 40
VOUT 41
VOUT 42
VOUT 43
VOUT 44
VOUT 45
VOUT 46
VOUT 47
VOUT 48
VOUT 49
VOUT 50
VOUT 51
VOUT 52
VOUT 53
PGND
54
PGND
55
VOUT PAD 2
VOUT PAD 1
PGND PAD 2
PVIN 56
PVIN 57
PVIN 58
PVIN 59
PVIN 60
PVIN 61
PVIN 62
PVIN PAD
BST 63
BST 64
ILIM 65
EN/MODE 66
AGND 67
TON 68
AGND PAD
BST PAD
GL PAD
12VIN
500kHz, 15A@1.2VOUT
R1
2k
R2
2k
R5 10k
CVIN
0.1uF
2x22uF
RON
8.87k
PVIN
680uF
SW
RLIM
2.49k
3x47uF
RSNB
1 Ohm
CSNB
1nF
VCC
FB
CSS
47nF
PVIN
© 2014 Exar Corporation
XR79115
16 / 19 exar.com/XR79115
Rev 1B
Mechanical Dimensions
© 2014 Exar Corporation
XR79115
17 / 19 exar.com/XR79115
Rev 1B
© 2014 Exar Corporation
XR79115
18 / 19 exar.com/XR79115
Rev 1B
© 2014 Exar Corporation
XR79115
19 / 19 exar.com/XR79115
Rev 1B
For Further Assistance:
Technical Support: techsupport.exar.com
Technical Documentation: www.exar.com/techdoc
Exar Corporation Headquarters and Sales Offices
48720 Kato Road Tel.: +1 (510) 668-7000
Fremont, CA 95438 - USA Fax: +1 (510) 668-7001
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 herein 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 Cor-
poration is adequately protected under the circumstances.
Reproduction, in part or whole, without the prior written consent of EXAR Corporation is prohibited.
Ordering Information
“YY” = Year (last two digits)- “WW” = Work Week- “X” = Lot Number; when applicable
Revision History
Part Number Package JEDEC
Compliant
Operating Temperature
Range
Packaging Quantity Marking
XR79115EL-F
12x12mm QFN Yes -40°C to +125°C
Tray XR79115EL
YYWWF
XXXXXXXX
XR79115ELTR-F Tape and Reel
XR79115EVB XR79115 Evaluation Board
Revision Date Description
1A December 2014 ECN 1451-09
1B January 2015 Corrected schematic on page 1, ECN 1504-06
