PD-97472
IR3871MPBF
SupIRBuck
Features
TM
8A HIGHLY INTEGRATED
WIDE-INPUT VOLTAGE, SYNCHRONOUS BUCK REGULATOR
Description
The IR3871
SupIRBuck
TM
is an easy-to-use,
fully integrated and highly efficient DC/DC
voltage regulator. The onboard constant on time
hysteretic controller and MOSFETs make
IR3871 a space-efficient solution that delivers up
to 8A of precisely controlled output voltage in
60°C ambient temperature applications without
airflow.
Programmable switching frequency, soft start,
and over current protection allows for a very
flexible solution suitable for many different
applications and an ideal choice for battery
powered applications.
Additional features include pre-bias startup, very
precise 0.5V reference, over/under voltage shut
down, power good output, and enable input with
voltage monitoring capability.
Input Voltage Range: 3V to 26V
Output Voltage Range: 0.5V to 12V
Continuous 8A Load Capability
Constant On-Time control
Excellent Efficiency at very low output current levels
Compensation Loop not required
Programmable switching frequency, soft start, and
over current protection
Power Good Output
Precision Voltage Reference (0.5V, +/-1%)
Pre-bias Start Up
Under/Over Voltage Fault Protection
Ultra small, low profile 5 x 6mm QFN Package
Applications
Notebook and desktop computers
Game consoles
Consumer electronics – STB, LCD, TV, printers
General purpose POL DC-DC converters
1
IR3871MPBF
ABSOLUTE MAXIMUM RATINGS
(Voltages referenced to GND unless otherwise specified)
•
•
•
•
•
•
•
•
•
•
•
•
VIN. FF …………………………………………..……. -0.3V to 30V
VCC, PGood, EN ………………….…....….…..….… -0.3V to 8.0V
Boot ……………………………………..……..…...…. -0.3V to 40V
PHASE ……………………………………………....... -0.3V to 30V(DC), -5V(100ns)
Boot to PHASE …..………………………………..….. -0.3V to 8V
ISET …………………………………………..….……. -0.3V to 30V
PGND to GND ……………...……………..………….. -0.3V to +0.3V
All other pins ……………...………………….……….. -0.3V to 3.9V
Storage Temperature Range ................................... -65°C To 150°C
Junction Temperature Range ................................... -40°C To 150°C
ESD Classification …………………………….……… JEDEC Class 1C
Moisture sensitivity level ……….……...…………..… JEDEC Level 2 @ 260°C (Note 2)
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
5mm x 6mm POWER QFN
θ
JA
=
35
o
C / W
θ
J
-
PCB
=
2
o
C / W
ORDERING INFORMATION
PKG DESIG
M
M
PACKAGE
DESCRIPTION
IR3871MTRPbF
IR3871MTR1PbF
PIN COUNT
17
17
PARTS PER
REEL
4000
750
2
IR3871MPBF
Simplified Block Diagram
3
IR3871MPBF
Pin Description
NAME
NC
ISET
PGOOD
GND
FB
SS
NUMBER
1
2
3
4,17
5
6
5V
Reference
3.3V
3.3V
I/O
LEVEL
-----
DESCRIPTION
No connection.
Connecting resistor to PHASE pin sets over current trip point.
Power good open drain output – pull up with a resistor to 3.3V.
Bias return and signal reference.
Inverting input to PWM comparator, OVP / PGood sense.
Soft start/shutdown. This pin provides user programmable soft-
start function. Connect an external capacitor from this pin to
GND to set the startup time of the output voltage. The converter
can be shutdown by pulling this pin below 0.3V.
No connection.
LDO output. A minimum of 1.0 µF ceramic capacitor is required
from 3VCBP to GND.
No connection.
Gate drive supply. A minimum of 1.0µF ceramic capacitor must
be connected from this pin to the power return (PGND).
Power return.
Phase node (or switching node) of MOSFET half bridge.
Input voltage for the system.
Bootstrapped gate drive supply – connect a capacitor to
PHASE.
Input voltage feed forward – sets on-time with a resistor to VIN.
Enable pin to turn on and off the device. Use two external
resistors to set the turn on threshold (see
Electrical
Specifications)
for input voltage monitoring.
NC
3VCBP
NC
VCC
PGND
PHASE
VIN
BOOT
FF
EN
7
8
9
10
11
12
13
14
15
16
-----
3.3V
-----
5V
Reference
VIN
VIN
VIN +VCC
VIN
5V
4
IR3871MPBF
Recommended Operating Conditions
Symbol
VIN
VCC
V
OUT
I
OUT
Fs
T
J
Definition
Input Voltage
Supply Voltage
Output Voltage
Output Current
Switching Frequency
Junction Temperature
Min
3
4.5
0.5
0
N/A
0
Max
26*
7.5
12
8
1000
125
Unit
V
A
kHz
o
C
*
PHASE pin must not exceed 30V.
Electrical Specifications
Unless otherwise specified, these specification apply over VIN = 12V, VCC = 5V, 0
o
C ≤ T
J
≤ 125
o
C.
PARAMETER
BIAS SUPPLIES
VCC Turn-on Threshold
VCC Turn-off Threshold
VCC Threshold Hysteresis
VCC Operating Current
VCC Shutdown Current
FF Shutdown Current
VIN Shutdown Current
INTERNAL LDO OUTPUT
LDO Output Voltage Range
Output Current
CONTROL LOOP
Reference Accuracy, V
REF
On-Time Accuracy
Min Off Time
Soft-Start Current
Zero Current Threshold
FAULT PROTECTION
ISET Pin Output Current
Under Voltage Threshold
Under Voltage Hysteresis
Over Voltage Threshold
Over Voltage Hysteresis
PGOOD Delay Threshold
(V
SS
)
1
1
1
1
EN = HIGH
Measure at V
PHASE
8
-5
18
0.37
0.58
NOTE
TEST CONDITION
MIN
3.9
3.6
R
FF
= 200K,
EN = HIGH, Fs = 300kHz
EN = LOW
EN = LOW
EN = LOW
C
3VCBP
= 1µF
3.1
TYP
4.2
3.9
150
7.1
35
2
1
3.3
MAX
4.5
4.2
UNIT
V
V
mV
mA
µA
µA
µA
V
mA
V
ns
ns
µA
mV
µA
V
mV
0.66
V
mV
V
50
3.5
8
V
REF
R
FF
= 180K, T
J
= 65
o
C
0.495
280
0.5
300
400
10
-2.4
20
0.4
10
0.62
10
1
0.505
320
12
0
22
0.43
Falling V
FB
& Monitor PGOOD
Rising V
FB
Rising V
FB
& Monitor PGOOD
Falling V
FB
5
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