LTC3716EG Linear Technology, LTC3716EG Datasheet - Page 24

• Manufacturer Part Number: LTC3716EG
• Description: IC SW REG STP-DN 5BIT SYNC36SSOP
• Manufacturer: Linear Technology
• Type: Step-Down (Buck)r

Specifications of LTC3716EG

• Internal Switch(s): No
• Synchronous Rectifier: Yes
• Number Of Outputs: 1
• Voltage - Output: 0.6 ~ 1.75 V
• Current - Output: 35mA
• Frequency - Switching: 120kHz ~ 310kHz
• Voltage - Input: 4 ~ 36 V
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 36-SSOP
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant
• Power - Output: -

APPLICATIO S I FOR ATIO
LTC3716
The worst-case power disipated by the synchronous
MOSFET under normal operating conditions at elevated
ambient temperature and estimated 50 C junction tem-
perature rise is:
A short-circuit to ground will result in a folded back current
of about:
The worst-case power disipated by the synchronous
MOSFET under short-circuit conditions at elevated ambi-
ent temperature and estimated 50 C junction temperature
rise is:
which is less than normal, full-load conditions. Inciden-
tally, since the load no longer dissipates power in the
shorted condition, total system power dissipation is de-
creased by over 99%.
The duty factor for this application is:
Using Figure 4, the RMS ripple current will be:
24
I
P
P
I
P
DF
SC
INRMS
MAIN
SYNC
SYNC
V
0 004
V
= (20A)(0.25) = 5A
25
IN
.
O
0 013
1 2
5 5
1 5
696
300
5 5
5 5
.
mV
.
.
.
.
.
W
1 2
V
V
V
V
5 5
5 5
mW
kHz
5
.
.
.
V
10
V
V
V
U
1 2
1 2
2
1
.
.
2
1 7 5 5
V
V
0 24
.
200
1
0 45
.
2 10
.
U
6 8
ns
.
.
1
0 005 110
W
RMS
A
.
V
A
H
5 5
2
2
.
2
1 48 0 013
10
V
1 48 0 013
W
.
.
A
300
6 8
C
.
.
.
A
pF
25
U
C
An input capacitor(s) with a 5A
required.
The output capacitor ripple current is calculated by using
the inductor ripple already calculated for each inductor
and multiplying by the factor obtained from Figure 3
along with the calculated duty factor. The output ripple in
continuous mode will be highest at the maximum input
voltage since the duty factor is < 50%. The maximum
output current ripple is:
PC Board Layout Checklist
When laying out the printed circuit board, the following
checklist should be used to ensure proper operation of the
LTC3716. Check the following in your layout:
1) Are the signal and power grounds separate? The signal
ground traces should return to Pin 9 first. Connect Pin 9
to Pin 28 through a wide and straight trace. Then the signal
ground joins the power ground plane beside Pin 28. It is
recommended that the Pin 28 return to the (–) plates of
C
2) Does the LTC3716 V
load? Does the LTC3716 V
return?
IN
TRACE TO INDUCTOR
V
.
OUTRIPPLE
I
I
COUT
COUTMAX
Figure 10. Proper Current Sense Connections
V
OUT
fL
2
20
PADS OF SENSE RESISTOR
300
A
SENSE
m
0 5
P P
-
.
kHz
1 2
+
OS
at
2
.
A
+
24
V
P P
1 0
SENSE
OS
pin connect to the point of
-
.
%
RMS
–
pin connect to the load
D F
–
H
ripple current rating is
40
0 5
.
mV
TRACE TO OUTPUT CAP (+)
P P
-
3716 F10