PD-97506
IR3856WMPbF
SupIRBuck
Features
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TM
HIGHLY EFFICIENT
Description
The IR3856W
SupIRBuck
TM
is an easy-to-use,
fully integrated and highly efficient DC/DC
synchronous Buck regulator. The MOSFETs co-
packaged with the on-chip PWM controller make
IR3856W a space-efficient solution, providing
accurate power delivery for low output voltage
applications.
IR3856W is a versatile regulator which offers
programmability of start up time, switching
frequency and current limit while operating in
wide input and output voltage range.
The switching frequency is programmable from
250kHz to 1.5MHz for an optimum solution.
It also features important protection functions,
such as Pre-Bias startup, hiccup current limit and
thermal shutdown to give required system level
security in the event of fault conditions.
INTEGRATED 6A, SYNCHRONOUS BUCK REGULATOR
Greater than 95% Maximum Efficiency
Wide Input Voltage Range 1.5V to 16V
Wide Output Voltage Range 0.7V to 0.9*Vin
Continuous 6A Load Capability
Integrated Bootstrap-diode
High Bandwidth E/A for excellent transient
performance
Programmable Switching Frequency up to 1.5MHz
Programmable Over Current Protection
PGood output
Hiccup Current Limit
Precision Reference Voltage (0.7V, +/-1%)
Programmable Soft-Start
Enable Input with Voltage Monitoring Capability
Enhanced Pre-Bias Start-up
Seq input for Tracking applications
-40
o
C to 125
o
C operating junction temperature
Thermal Protection
4mm x 5mm Power QFN Package
Halogen Free, Lead Free and RoHS compliant
Server Applications
Storage Applications
Embedded Telecom Systems
Distributed Point of Load Power Architectures
Applications
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Netcom Applications
Computing Peripheral Voltage Regulators
General DC-DC Converters
Fig. 1. Typical application diagram
Rev 9.0
1
PD-97506
IR3856WMPbF
ABSOLUTE MAXIMUM RATINGS
(Voltages referenced to GND unless otherwise specified)
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Vin ……………………………………….……………. -0.3V to 25V
PVcc, Vcc ……………….……..….……..……….…… -0.3V to 8V
(Note2)
Boot
SW
……………………………………..……….…. -0.3V to 33V
…………………………………………..……… -0.3V to 25V(DC), -4V to 25V(AC, 100ns)
……..…………………………….…..….. -0.3V to Vcc+0.3V
(Note1)
Boot to SW
OCSet
………………………………………….……. -0.3V to 30V (Max 30mA)
……………………………….. ... -0.3V to Vcc+0.3V
(Note1)
Input / output Pins
PGND to GND ……………...………………………….. -0.3V to +0.3V
Storage Temperature Range ................................... -55°C To 150°C
Junction Temperature Range ................................... -40°C To 150°C
(Note2)
ESD Classification …………………………… ……… JEDEC Class 1C
Moisture sensitivity level………………...………………JEDEC Level 3@260 °C
(Note5)
Note1:
Must not exceed 8V
Note2:
Vcc must not exceed 7.5V for Junction Temperature between -10
o
C and -40
o
C
Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to
the device. These are stress ratings only and functional operation of the device at these or any other
conditions beyond those indicated in the operational sections of the specifications are not implied.
PACKAGE INFORMATION
4mm x 5mm POWER QFN
13
V
IN
12
SW
11
PGnd
θ
JA
( Sync _ FET )
=
45
o
C / W
*
θ
JA
( Ctrl _ FET )
=
45
o
C / W
*
θ
J
-
PCB
=
2
o
C / W
*
Boot
Enable
Seq
14
15
16
1
Fb
10
17
Gnd
PVcc
V
CC
PGood
9
8
Exposed pads on underside
are connected to copper
pads of 4-layer (2 oz.) PCB
board design
2
3
4
5
6
7
NC COMP Gnd Rt SS/SD OCSet
ORDERING INFORMATION
PACKAGE
DESIGNATOR
M
M
Rev 9.0
PACKAGE
DESCRIPTION
IR3856WMTRPbF
IR3856WMTR1PbF
PIN COUNT
17
17
PARTS PER
REEL
4000
750
2
PD-97506
IR3856WMPbF
Block Diagram
Fig. 2. Simplified block diagram of the IR3856W
Rev 9.0
3
PD-97506
IR3856WMPbF
Pin Description
Pin
1
2
3
4
5
6
Name
Fb
NC
Comp
Gnd
Rt
SS/SD
Description
Inverting input to the error amplifier. This pin is connected directly to the
output of the regulator via resistor divider to set the output voltage and
provide feedback to the error amplifier.
No connect
Output of error amplifier. An external resistor and capacitor network is
typically connected from this pin to Fb pin to provide loop
compensation.
Signal ground for internal reference and control circuitry.
Set the switching frequency. Connect an external resistor from this pin
to Gnd to set the switching frequency.
Soft start / shutdown. This pin provides user programmable soft-start
function. Connect an external capacitor from this pin to Gnd to set the
start up time of the output voltage. The converter can be shutdown by
pulling this pin below 0.3V.
Current limit set point. A resistor from this pin to SW pin will set the
current limit threshold.
Power Good status pin. Output is open drain. Connect a pull up resistor
from this pin to Vcc.
This pin powers the internal IC. A minimum of 1uF high frequency
capacitor must be connected from this pin to Analog ground (AGnd).
This pin powers the drivers. A minimum of 1uF high frequency capacitor
must be connected from this pin to the power ground (PGnd).
Power Ground. This pin serves as a separated ground for the MOSFET
drivers and should be connected to the system’s power ground plane.
Switch node. This pin is connected to the output inductor.
Input voltage connection pin.
Supply voltage for high side driver. A 0.1uF capacitor must be
connected from this pin to SW.
Enable pin to turn on and off the device. Use two external resistors to
set the turn on threshold (see Enable section). Connect this pin to Vcc if
it is not used.
Sequence pin. Use two external resistors to set Simultaneous Power up
sequencing. If this pin is not used connect to Vcc.
Signal ground for internal reference and control circuitry.
7
8
9
10
11
12
13
14
15
16
17
OCSet
PGood
V
CC
PVcc
PGnd
SW
V
IN
Boot
Enable
Seq
Gnd
Rev 9.0
4
PD-97506
IR3856WMPbF
Recommended Operating Conditions
Symbol
V
in
P V
cc
, V
cc
Boot to SW
V
o
I
o
Fs
T
j
Definition
Input Voltage
Supply Voltage
Supply Voltage
Output Voltage
Output Current
Switching Frequency
Junction Temperature
Min
1.5
4.5
4.5
0.7
0
225
-40
Max
16
5.5
5.5
0.9*Vin
6
1650
125
Units
V
A
kHz
o
C
Electrical Specifications
Unless otherwise specified, these specification apply over 4.5V< PVcc=V
cc
<5.5V, V
in
=12V
0
o
C<T
j
< 125
o
C. Typical values are specified at T
a
= 25
o
C.
Parameter
Power Loss
Power Loss
P
loss
Vcc=5V, V
in
=12V, V
o
=1.8V, I
o
=6A,
Fs=600kHz, L=0.82uH,
Note4
1.3
W
Symbol
Test Condition
Min
TYP
MAX
Units
MOSFET R
ds(on)
Top Switch
Bottom Switch
R
ds(on)_Top
R
ds(on)_Bot
V
Boot
-V
sw
=5V, I
D
=6A, Tj=
25 C
V
cc
=5V, I
D
=6A, Tj=
25 C
o
o
22.6
14.3
29.0
19
mΩ
Reference Voltage
Feedback Voltage
Accuracy
V
FB
0 C<Tj<125 C
-40 C<Tj<125 C,
Note3
o
o
o
o
0.7
-1.0
+2.0
+1.0
V
%
+2.0
Supply Current
V
CC
Supply Current (Standby)
V
cc
Supply Current (Dyn)
PV
CC
Supply Current (Standby)
PV
cc
Supply Current (Dyn)
I
CC(Standby)
I
CC(Dyn)
I
PCC(Standby)
I
PCC(Dyn)
SS=0V, No Switching, Enable low
SS=3V, Vcc=5V, Fs=500kHz
Enable high
SS=0V, No Switching, Enable low
SS=3V, PVcc=5V, Fs=500kHz
Enable high
3
6
7
500
μA
mA
μA
mA
Under Voltage Lockout
V
CC
-Start-Threshold
V
CC
-Stop-Threshold
Enable-Start-Threshold
Enable-Stop-Threshold
Enable leakage current
V
CC
_UVLO_Start
V
CC
_UVLO_Stop
Enable_UVLO_Start
Enable_UVLO_Stop
Ien
Vcc Rising Trip Level
Vcc Falling Trip Level
Supply ramping up
Supply ramping down
Enable=3.3V
3.95
3.65
1.14
0.9
4.15
3.85
1.2
1.0
4.35
4.05
1.36
1.06
15
μA
V
Rev 9.0
5
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