LTC3855IFE#PBF Linear Technology, LTC3855IFE#PBF Datasheet - Page 34

• Manufacturer Part Number: LTC3855IFE#PBF
• Description: IC CTLR DC/DC MULTIPHASE 38SSOP
• Manufacturer: Linear Technology
• Series: PolyPhase®r
• Type: Step-Down (Buck)r

Specifications of LTC3855IFE#PBF

• Internal Switch(s): No
• Synchronous Rectifier: Yes
• Number Of Outputs: 2
• Voltage - Output: 0.6 ~ 3.3 V, 0.6 ~ 12.5 V
• Current - Output: 25A
• Frequency - Switching: 250kHz ~ 770kHz
• Voltage - Input: 4.5 ~ 38 V
• Operating Temperature: -40°C ~ 125°C
• Mounting Type: Surface Mount
• Package / Case: 38-TSSOP Exposed Pad, 38-eTSSOP, 38-HTSSOP
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Power - Output: -

LTC3855
applicaTions inForMaTion
MOSFET results in: R
2.6V, C
(estimated) = 75°C:
For a 2mΩ sense resistor, a short-circuit to ground will
result in a folded back current of:
Typical applicaTions
R

NTC2
100k
P
I
(
= 329mW + 288mW
= 617mW



SC
0.013Ω
L1, L2: VISHAY IHLP5050CE-01, 0.68µH
C
C
RNTC1, RNTC2: MURATA NCP18WF104J03RB
MAIN
5V – 2.6V
OUT1
OUT2
20k
15k
20k
=
100pF
100pF
MILLER
0.1µF
, C
, C
OUT3
OUT4
(
1
=
49.9k
0.1µF
1/ 3
1nF
1nF
0.002Ω
: MURATA GRM32ER60J107ME20
: KEMET T520V337M004ATE009
1.8V
20V
Figure 18. 2.5V, 15A and 1.8V, 15A Supply with NTC Temperature Compensated DCR Sensing, f
)
+ 20V
R
)
≅ 150pF . At maximum input voltage with T
100k
NTC1
50mV
(
+
0.1µF
(
2.6V
15A
1
20k
)
20k
20k
40.2k
–
2
DS(ON)
)
63.4k
49.9k

 400kHz

2

 
2
1
(
[
15A

 
1+ (0.005)(75°C – 25°C)
2
90ns(20V)
0.56µH
TK/SS1
I
V
SGND
V
I
TK/SS2
SENSE2
SENSE2
DIFFP
TH1
TH2

 
= 13mΩ (max), V
FB1
FB2
( )
2Ω
0.1µF
+
–
)
(
PGOOD1
PGOOD2
150pF

 
LTC3855
= 6.7A
)
•
86.6k
MILLER
100k
100k
]
BOOST1
BOOST2
EXTV
INTV
•
PGND1
PGND2
TG1
BG1
BG2
V
CC
CC
IN
=
J
0.1µF
A Renesas RJK0330DPB, R
the bottom FET. The resulting power loss is:
C
temperature assuming only channel 1 or 2 is on. C
chosen with an equivalent ESR of 4.5mΩ for low output
ripple. The output ripple in continuous mode will be highest
at the maximum input voltage. The output voltage ripple
due to ESR is approximately:
Further reductions in output voltage ripple can be made
by placing a 100µF ceramic across C
4.7µF
0.1µF
IN
P
V
P
 
is chosen for an RMS current rating of at least 7.5A at
SYNC
ORIPPLE
SYNC
1+ 0.005
CMDSH-3
CMDSH-3
(
0.1µF
2.2
= 1W
=
20V – 1.8V
= R
)
20V
ESR
• 75°C – 25°C
(
M1
RJK0305DPB
M2
RJK0330DPB
M3
RJK0305DPB
M4
RJK0330DPB
(∆I
L
(
) = 0.0045Ω • 6.8A = 31mV
10µF
15A
2
DS(ON)
3.01k
3.01k
)
0.68µH
0.68µH
24.9k
24.9k
2
L1
L2
)
•
  • 0.0039Ω
SW
= 3.9mΩ, is chosen for
= 350kHz
OUT
+
3855 F18
82µF
25V
C
100µF
6.3V
C
100µF
6.3V
.
2
OUT1
OUT3
+
+
C
330µF
4V
C
330µF
4V
OUT2
2
OUT4
2
OUT
P–P
V
4.5V TO
20V
V
2.5V
15A
V
1.8V
15A
IN
OUT1
OUT2
3855f
is