LTC3736EGN-1 Linear Technology, LTC3736EGN-1 Datasheet - Page 19

• Manufacturer Part Number: LTC3736EGN-1
• Description: IC CTRLR SW SYNC DUAL 2PH 24SSOP
• Manufacturer: Linear Technology
• Series: PolyPhase®r
• Type: Step-Down (Buck)r

Specifications of LTC3736EGN-1

• Internal Switch(s): No
• Synchronous Rectifier: Yes
• Number Of Outputs: 2
• Voltage - Output: 0.6 ~ 9.8 V
• Current - Output: 1A
• Frequency - Switching: 450kHz ~ 580kHz
• Voltage - Input: 2.75 ~ 9.8 V
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 24-SSOP
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant
• Power - Output: -

APPLICATIO S I FOR ATIO
The ramp time for V
is:
For coincident tracking,
where V
V
OUT1
t
t
SS
SS
2
2
and V
Figures 8b and 8c. Two Different Modes of Output
OUT1F
=
=
t
t
SS
SS
OUT2
1
1
and V
Figure 8a. Using the TRACK Pin
R
R
•
•
TRACKB
TRACKA
R
V
V
. V
OUT F
TRACKA
OUT F
(8c) Ratiometric Tracking
(8b) Coincident Tracking
R A
U
OUT2F
OUT2
OUT1
1
Voltage Tracking
2
1
V
OUT1
R1B
R1A
to rise from 0V to its final value
U
are the final, regulated values of
should always be greater than
•
TIME
TIME
R
V
TRACK
LTC3736-1
FB1
TRACKA
R A R B
V
FB2
1
W
37361 F08a
37361 F08b,c
V
+
+
OUT2
R
R2B
R2A
V
V
V
V
1
TRACKB
OUT1
OUT2
OUT1
OUT2
U
V
is desired, then the TRACK pin may be tied to V
ever, in this situation there would be no (internal nor
external) soft-start on V
When using tracking with spread spectrum operation
enabled, the tracking resistors R
should have value at least 10 times smaller than corre-
sponding feedback resistors R2A and R2B.
Fault Condition: Short Circuit and Current Limit
To prevent excessive heating of the bottom MOSFET,
foldback current limiting can be added to reduce the
current in proportion to the severity of the fault.
Foldback current limiting is implemented by adding di-
odes D
shown in Figure 9. In a hard short (V
will be reduced to approximately 50% of the maximum
output current.
Low Supply Operation
Although the LTC3736-1 can function down to below
2.4V, the maximum allowable output current is reduced as
V
OUT2
IN
decreases below 3V. Figure 10 shows the amount of
when using the TRACK pin. If no tracking function
FB1
Maximum Sense Voltage for Low Input Supply
and D
Figure 10. Line Regulation of V
105
100
Figure 9. Foldback Current Limiting
95
90
85
80
75
2.0
FB2
2.1
V
2.2
1/2 LTC3736-1
I
REF
between the output and the I
TH
2.3
INPUT VOLTAGE (V)
MAXIMUM
SENSE VOLTAGE
OUT2
2.4
V
FB
2.5
.
2.6
R2
R1
2.7
+
2.8
TRACKA
OUT
2.9
37361 F10
LTC3736-1
REF
37361 F09
3.0
= 0V), the current
D
D
FB1
FB2
V
and
OUT
and R
TH
IN
19
TRACKB
. How-
pin as
37361f