IR3865MTRPBF International Rectifier, IR3865MTRPBF Datasheet - Page 16

• Manufacturer Part Number: IR3865MTRPBF
• Description: IC BUCK SYNC ADJ 10A PQFN
• Manufacturer: International Rectifier
• Series: SupIRBuck™r
• Type: Step-Down (Buck), PWMr

Specifications of IR3865MTRPBF

• 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 ~ 21 V
• Operating Temperature: -40°C ~ 125°C
• Mounting Type: *
• Package / Case: *
• Primary Input Voltage: 21V
• No. Of Outputs: 1
• Output Voltage: 12V
• Output Current: 10A
• No. Of Pins: 17
• Operating Temperature Range: -40°C To +125°C
• Msl: MSL 3 - 168 Hours
• 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 - 21
• 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
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

DESIGN EXAMPLE
Design Criteria:
Input Voltage, VIN = 7V to 16V
Output Voltage, VOUT = 1.5V
Switching Frequency, Fs = 300kHz
Inductor Ripple Current, 2ΔI = 2A
Maximum Output Current, IOUT = 10A
Over Current Trip, IOC = 15A
Overshoot Allowance for 5A Load Step Down,
VOS = VOUT + 75mV
Undershoot Allowance for 5A Load Step Up,
VDROP = 75mV
Find R
Pick a standard value 255 kΩ, 1% resistor.
Find R
Pick a 8.45kΩ, 1% standard resistor.
Find a resistive voltage divider for V
R
resistors.
Choose the soft start capacitor:
Once the soft start time has chosen, such as
1000us to reach to the reference voltage, a
22nF for C
Choose an inductor to meet the design
specification:
Choose an inductor with the lowest DCR and
AC power loss as possible to increase the
overall system efficiency. For instance, choose
a
CYNTEC. The inductance of this part is 2.2µH
and has 6.0mΩ DCR. Ripple current needs to
be recalculated using the chosen inductor.
2
2/16/2011 Rev2.3
= 1.40kΩ, R
PIMB104T-2R2MS-39
R
FF
SET
R
FF
SET
:

V
:
SS
1
FB

L
V
is used to meet 1000µs.
10.7m





1
20
R
1.5
2.3
16
V
= 2.80 kΩ, both 1% standard
R
2
pF
OUT
1.5
V

V
9 1
2

V


H
R
IN

V


2


300k

1
16


A
A
V
15

2
V

V
IN
ΔI
300k
A
OUT

-
Hz
manufactured

1.5
V
F

OUT
s
Hz

V

0.5
2

8.4k

OUT
50
V
k
= 1.5V:


by
I
IN_RMS
Choose an input capacitor:
A
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
specification, equation 7b and 8 will be used to
calculate the minimum output capacitance. As a
result, 240µF will be needed for 5A load
removal. To meet the stability requirement,
choose an output capacitors with ESR larger
than 10mΩ. Combine those two requirements,
one can choose a set of output capacitors from
manufactures
Polymer Capacitor) from Panasonic or POSCAP
from Sanyo. A 330µF (EEFUE0E331XR) from
Panasonic with 10mΩ 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 Consideration Section.
In this design example, we can choose C14 =
1nF and C13 = 100nF. To calculate the value of
R6 with PIMB104T-2R2MS-39 as our inductor:
Pick a standard value for R6 = 3.65kΩ.

meet
2Δ
Panasonic
10
I
A


6 1
R
the
1.5
6
V
1.5
6 1



such

V
V
V
2
. 3
6
DCR
undershoot
2 .

0 .
67


10µF
6 1

m
H
2
L
k
1
V
as

2 .




C
-
300k


1.5
1
3
13
100
H
IR3865MBF
SP-Cap

V



(ECJ3YB1E106M)
2
nF
Hz

1 .
and
10
A

A
2 /
2.1
overshoot
(Specialty



A
2

16
3
1 .
A