IR3477MTR1PBF International Rectifier, IR3477MTR1PBF Datasheet - Page 16

• Manufacturer Part Number: IR3477MTR1PBF
• Description: IC BUCK SYNC ADJ 15A PQFN
• Manufacturer: International Rectifier
• Series: SupIRBuck™r
• Type: Step-Down (Buck), PWM - Current Moder

Specifications of IR3477MTR1PBF

• Internal Switch(s): Yes
• Synchronous Rectifier: Yes
• Number Of Outputs: 1
• Voltage - Output: 0.5 V ~ 12 V
• Current - Output: 15A
• Frequency - Switching: Up to 750kHz
• Voltage - Input: 3 V ~ 27 V
• Operating Temperature: -40°C ~ 125°C
• Mounting Type: *
• Package / Case: *
• Part Status: Preferred
• Package: PQFN / 5 x 6
• Circuit: Single Output
• Iout (a): 15
• Switch Freq (khz): 0 - 750
• Input Range (v): 3.0 - 27
• Output Range (v): 0.5 - 12
• Ocp Otp Uvlo Pre-bias Soft Start And: Constant On-Time + PGOOD + EN + Temp Comp OCP
• Digital Home Media: Yes
• Mobile Computing: Yes
• Industrial 24v Input: Yes
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

DESIGN EXAMPLE
DESIGN CRITERIA
Find R
Pick a standard value 158 kΩ, 1% resistor.
Find RSET:
Pick a 7.15kΩ, 1% standard resistor.
Find a resistive voltage divider for V
R
Choose the soft start capacitor:
Once the soft start time has chosen, such as 1000us to
reach to the reference voltage, a 22nF for CSS is used to
meet 1000us.
Choose an inductor to meet the design specification:
Choose the inductor with the lowest DCR and AC power
2
= 1.33kΩ, R
 Input Voltage, VIN = 6V to 21V
 Output Voltage, VOUT = 1.25V
 Switching Frequency, Fs = 400kHz
 Inductor Ripple Current, 2ΔI = 3A
 Maximum Output Current, IOUT = 12A
 Over Current Trip, IOC = 18A
 Current Transient Step Size = 5A
 Overshoot Allowance, VOS = VOUT + 50mV
 Undershoot Allowance, VDROP = 50mV
FF
:
R
FF
R
L
V
SET

16
FB
1



1
= 1.96 kΩ, both 1% standard resistors.
V

1.0
1.25

V
7.5m

21
OUT
R
20
February 16, 2011 | ADVANCED DATASHEET | V2.0 | PD97604

V
V
R
2
V
H
1.25
IN

pF
2


9 1



3
R

V

2
21
A


1
IN
V
ΔI

400k
18

A

V
V

400k

V
A
-
OUT
F
1.25
OUT
s
Hz

Hz
OUT

V

0.5

= 1.25V:
7.1k

156
V

k

15A Highly Integrated SupIRBuck
loss as possible to increase the overall system efficiency.
For instance, choose a PIMB103E‐1R0MS‐39 manufactured
by CYNTEC. The inductance of this part is 1µH and has
2.7mΩ DCR. Ripple current needs to be recalculated using
the chosen inductor.
Choose an input capacitor:
A Panasonic 10µF (ECJ3YB1E106M) accommodates 6 Arms
of ripple current at 300kHz. Due to the chemistry of
multilayer ceramic capacitors, the capacitance varies over
temperature and operating voltage, both AC and DC. One
10µF capacitor is recommended. In a practical solution,
one 1µF capacitor is required along with 10µF. The
purpose of the 1µF capacitor is to suppress the switching
noise and deliver high frequency current.
Choose an output capacitor:
To meet the undershoot and overshoot specification,
equations 7b and 8 will be used to calculate the minimum
output capacitance. As a result, 200μF will be needed for
5A load removal. To meet the stability requirement,
choose an output capacitor with ESR larger than 6mΩ.
Combine those two requirements, one can choose a set of
output capacitors from manufactures such as SP‐Cap
(Specialty Polymer Capacitor) from Panasonic or POSCAP
from Sanyo. A 220μF (EEFSL0D221R) from Panasonic with
9mΩ ESR will meet both requirements.
If an all ceramic output capacitor solution is desired, the
external slope injection circuit composed of R6, C13, and
C14 is required as explained in the Stability Considerations
section. In this design example, we can choose C14 = 1nF
and C13 = 100nF. To calculate the value of R6 with
PIMB103E‐1R0MS‐39 as our inductor:
Pick a standard value for R6 = 3.74kΩ.
I
IN_RMS
2Δ

I
2 1

A
1.25
21

R
V
6
V
1.25

21



1



V
3
2
DCR
21
V
H
7 .
7 .
V
k

m


L
400k
1
-

TM

1
1.25

C


H
13
100
1
3
Hz
V




nF

1
2 1

5 .
IR3477
3
A
A
A



2

2
9 .
A