IR3475MTR1PBF International Rectifier, IR3475MTR1PBF Datasheet - Page 16

• Manufacturer Part Number: IR3475MTR1PBF
• Description: IC BUCK SYNC ADJ 10A PQFN
• Manufacturer: International Rectifier
• Series: SupIRBuck™r
• Type: Step-Down (Buck), PWM - Current Moder

Specifications of IR3475MTR1PBF

• Internal Switch(s): Yes
• Synchronous Rectifier: Yes
• Number Of Outputs: 1
• Voltage - Output: 0.5 V ~ 12 V
• Current - Output: 10A
• Frequency - Switching: Up to 750kHz
• Voltage - Input: 3 V ~ 27 V
• Operating Temperature: -40°C ~ 125°C
• Mounting Type: *
• Package / Case: *
• Primary Input Voltage: 27V
• No. Of Outputs: 1
• Output Voltage: 12V
• Output Current: 10A
• No. Of Pins: 17
• Operating Temperature Range: -40°C To +125°C
• Peak Reflow Compatible (260 C): Yes
• Rohs Compliant: Yes
• Leaded Process Compatible: Yes
• Part Status: Preferred
• Package: PQFN / 4 x 5
• Circuit: Single Output
• Iout (a): 10
• 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 10.5kΩ, 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 1000µs to
reach to the reference voltage, a 22nF for C
meet 1000µs.
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 = 2.5A
 Maximum Output Current, IOUT = 10A
 Over Current Trip, IOC = 15A
 Current Transient Step Size = 4A
 Overshoot Allowance, VOS = VOUT + 50mV
 Undershoot Allowance, VDROP = 50mV
FF
:
R
R
FF
L
V
SET
16

FB
1



= 1.96 kΩ, both 1% standard resistors.

1
1.18
1.25

V
V
21
13m
OUT
R

February 16, 2011 | ADVANCED DATASHEET | V1.8 | PD97602
V
V
20
R
2
V


IN


2
H

9 1
2.5
1.25


pF

R
V

2
21


1
IN
15
ΔI
A
A


V
V
400k
V


A

400k
V
-
OUT
F
1.25
OUT
s
Hz

OUT
Hz


V
0.5
0 1
= 1.25V:


156
V
.3k
SS
is used to

k

10A Highly Integrated SupIRBuck
loss as possible to increase the overall system efficiency.
For instance, choose a PIMB104T‐1R5MS‐39 manufactured by
CYNTEC. The inductance of this part is 1.5µH and has 3.8mΩ
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, 190μF will be needed for 4A
load removal. To meet the stability requirement, choose an
output capacitor with ESR larger than 9mΩ. 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
(4TPE220MIC2) from Sanyo with 18mΩ 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 PIMB104T‐
1R5MS‐39 as our inductor:
Pick a standard value for R6 = 3.92kΩ.
I
IN_RMS

2Δ
10
I
A


21
1.25
1.25
V
R
21
V

6
1.5
V
V





. 3

3
21
DCR

8 .
H
95
V
1
m

1
k
L

-
400k

5 .
TM

1.25

1
3
C


100
13

H



V
Hz
10
1

nF
A
A

IR3475



2
2
A

2
4 .
A