IR3856MTRPBF International Rectifier, IR3856MTRPBF Datasheet - Page 24

• Manufacturer Part Number: IR3856MTRPBF
• Description: IC BUCK SYNC ADJ 6A 17PQFN
• Manufacturer: International Rectifier
• Series: SupIRBuck™r
• Type: Step-Down (Buck)r

Specifications of IR3856MTRPBF

• Internal Switch(s): Yes
• Synchronous Rectifier: Yes
• Number Of Outputs: 1
• Voltage - Output: 0.7 ~ 18.9 V
• Current - Output: 6A
• Frequency - Switching: 250kHz ~ 1.5MHz
• Voltage - Input: 1.5 ~ 21 V
• Operating Temperature: -40°C ~ 125°C
• Mounting Type: Surface Mount
• Package / Case: 17-PowerVQFN
• Power - Output: 1.11W
• Primary Input Voltage: 21V
• No. Of Outputs: 1
• Output Voltage: 18.9V
• Output Current: 6A
• 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): 6
• Switch Freq (khz): 250 - 1500
• Input Range (v): 1.5 - 21
• Output Range (v): 0.7 - 0.9*Vin
• Ocp Otp Uvlo Pre-bias Soft Start And: PGOOD + EN + SEQ + OVP + SYNC
• Design Tool: Yes
• Server Storage: Yes
• Routers Switches: Yes
• Base Station Telecom: Yes
• Digital Home Media: Yes
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

Detailed calculation of compensation Type-III
C
C
Programming the Current-Limit
The Current-Limit threshold can be set by
connecting a resistor (R
to the OCSet pin. The resistor can be calculated
by using equation (4). This resistor R
be placed close to the IC.
The
coefficient and it should be considered for the
worst case operation.
Desired
F
F
Select
F
Select
Calculate
R
Select
Calculate
R
R
Select
R
I
Z
P
P
3
10
SET
3
4
8
9
Rev2.0
2
3
2
=
=
=
=
=
=
=
=
=
V
2
2
2
2
F
F
0.5
2
=
π
π
π
π
o
:
:
:
:
o
o
V
R
π
C
R
-
F
R
ref
*
*
*
*
I
V
DS(on)
*
L
Z
*
7
8
1
F
C
1
1
1
F
3
F
1
ref
Phase
1
C
F
(
P
o
Z
1
1
−
+
=
=
+
−
7
=
critical
R
R
1
s
=
1
3
C
7
*
sin
sin
2.2
*
sin
sin
4.02
1.65
*
10
*
3
=
*
. 0
*
L
7
F
,
R
R
R
o
F
,
300
*
Z
* 5
C
P
8
nF
V
*
3
2
3
R
Θ
Θ
Θ
Θ
;
)
3
2
has
C
in
;
;
R
-
8
kΩ
F
k
C
=
C
;
R
=
o
=
and
Margin
Z
Ω
9
4
3
and
kHz
10
2
*
R
1
R
567.1
=
V
=
=
. 7
10
=
;
OCSet
osc
2.56
10
327
63
R
a
8.82
C
R
=
R
8
.
4
;
94
130
DS
OCSET
R
9
kHz
=
kHz
:
pF
kΩ
positive
3
Θ
:
3.97
∗
(
nF,
=
on
kHz
I
,
=
, Ω
OCSet
1.63
70
) from the SW pin
)
Select
Select
kΩ
Select
Select
o
and
,
kΩ
..........
:
:
temperature
R
C
OCSET
:
:
9
3
R
C
=
=
10
4
2.55
270
=
=
.
must
(32)
10
130
pF
kΩ
nF
Ω
R
I
(50%
I
R
Setting the Power Good Threshold
Power Good threshold can be programmed by
using two external resistors (R5, R7 on Page 24).
The following formula can be used to set the
threshold:
Where: 0.85*Vref is reference of the internal
comparator, for IR3856.
V
threshold for power good, for this design it is
1.53V (i.e. 0.85*1.8V).
The PGood is an open drain output. Hence, it is
necessary to use a pull up resistor R
PGood pin to Vcc.
resistor must be chosen such as to limit the
current flowing into the PGood pin, when the
output voltage is not in regulation, to less than 5
mA. A typical value used is 10kΩ.
OCSet
SET
DS
OCSet
o(PGood_TH)
Select R
Using (24): R
Select R
(
on
≅
R
=
)
I
6
o
=
over
=
59.07
(
=
LIM
2.55
13
(
V
7
6
)
4 .
=2.55KOhm
=4.02KOhm
( o
0
=
is the selectable output voltage
.
PGood
nominal
μA
85
kΩ
mΩ
6
5
A
=3.97KOhm
*
*
V
*
(at
Select
_
1.5
ref
1.25
TH
)
F
IR3856MPbF
=
The value of the pull-up
s
−
=
9
output
1
=
1
* )
A
600
R
. 6
R
7
62
7
=
kHz)
. 2
mΩ
current
55
PD-97528
- -
(33)
kΩ
PG
)
24
from