LTC3829EFE#PBF Linear Technology, LTC3829EFE#PBF Datasheet - Page 28

• Manufacturer Part Number: LTC3829EFE#PBF
• Description: IC BUCK SYNC ADJ 38TSSOP
• Manufacturer: Linear Technology
• Type: Step-Down (Buck)r

Specifications of LTC3829EFE#PBF

• Internal Switch(s): No
• Synchronous Rectifier: Yes
• Number Of Outputs: 1
• Voltage - Output: 0.6 ~ 5 V
• 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
• Current - Output: -
• Power - Output: -

LTC3829
applicaTions inForMaTion
The LTC3829 allows the user to program how its output
ramps up and down by means of the TK/SS pins. Through
these pins, the output can be set up to either coincidentally
or ratiometrically track another supply’s output, as shown
in Figure 11. In the following discussions, V
to the LTC3829’s output as a master and V
another supply output as a slave. To implement the coinci-
dent tracking in Figure 11a, connect an additional resistive
divider to V
of the slave controller. The ratio of this divider should be
the same as that of the slave controller’s feedback divider
shown in Figure 12a. In this tracking mode, V
be set higher than V
tracking in Figure 11b, the ratio of the V

OUT1
and connect its mid-point to the TK/SS pin
TK/SS2
V
OUT1
(11a) Coincident Tracking
PIN
TO
OUT2
(12a) Coincident Tracking Setup
. To implement the ratiometric
TIME
R3
R4
Figure 12. Setup and Coincident and Ratiometric Tracking
R1
R2
Figure 11. Two Different Modes of Output Voltage Tracking
TO
V
PIN
FB1
OUT2
3829 F11a
V
V
V
PIN
FB2
divider should
OUT1
OUT2
TO
OUT2
OUT1
OUT1
refers to
R3
R4
refers
must
V
OUT2
be exactly the same as the master controller’s feedback
divider shown in Figure 12b . By selecting different resis-
tors, the LTC3829 can achieve different modes of tracking
including the two in Figure 11.
So which mode should be programmed? While either
mode in Figure 11 satisfies most practical applications,
some trade-offs exist. The ratiometric mode saves a pair
of resistors, but the coincident mode offers better output
regulation. Under ratiometric tracking, when the master
controller’s output experiences dynamic excursion (under
load transient, for example), the slave controller output
will be affected as well. For better output regulation, use
the coincident tracking mode instead of ratiometric.
V
TK/SS2
OUT1
(12b) Ratiometric Tracking Setup
PIN
TO
R1
R2
TO
V
PIN
(11b) Ratiometric Tracking
FB1
V
PIN
FB2
TO
TIME
R3
R4
3829 F12
V
OUT2
3829 F11b
V
V
OUT1
OUT2
3829f