LTC3829EFE#PBF Linear Technology, LTC3829EFE#PBF Datasheet - Page 30

• 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
4. EXTV
For applications where the main input power is 5V, tie
the V
pins to the 5V input with a 1Ω or 2.2Ω resistor as shown
in Figure 13 to minimize the voltage drop caused by the
gate charge current. This will override the INTV
regulator and will prevent INTV
due to the dropout voltage. Make sure the INTV
is at or exceeds the R
which is typically 4.5V for logic-level devices
Topside MOSFET Driver Supply (C
External bootstrap capacitors, C
pins supply the gate drive voltages for the topside MOSFETs.
Capacitor C
external diode D
When one of the topside MOSFETs is to be turned on, the
driver places the C
desired MOSFET. This enhances the MOSFET and turns on
the topside switch. The switch node voltage, SW, rises to
V
on, the boost voltage is above the input supply:
0
IN
For 3.3V and other low voltage regulators, efficiency
gains can still be realized by connecting EXTV
output-derived voltage that has been boosted to greater
than 4.7V.
V
and the BOOST pin follows. With the topside MOSFET
BOOST
IN
CC
and INTV
= V
connected to an output-derived boost network.
B
in the Functional Diagram is charged though
IN
Figure 13. Setup for a 5V Input
+ V
B
LTC3829
CC
from INTV
B
INTVCC
voltage across the gate source of the
INTV
pins together and tie the combined
DS(ON)
V
CC
IN
test voltage for the MOSFET
CC
C
4.7µF
B
CC
INTVCC
R
when the SW pin is low.
, connected to the BOOST
1Ω
VIN
from dropping too low
B
, D
+
B
3829 F13
)
C
5V
IN
CC
CC
CC
voltage
linear
to an
The value of the boost capacitor, C
that of the total input capacitance of the topside MOSFET(s).
The reverse breakdown of the external Schottky diode
must be greater than V
drive level, the final arbiter is the total input current for
the regulator. If a change is made and the input current
decreases, then the efficiency has improved. If there is
no change in input current, then there is no change in
efficiency.
Setting Output Voltage
The LTC3829 output voltage is set by an external feed-
back resistive divider carefully placed across the output,
as shown in Figure 14. The regulated output voltage is
determined by:
To improve the frequency response, a feedforward ca-
pacitor, C
route the V
inductor or the SW line.
If diffamp is used, then the resistor, R
to the output of the diffamp, DIFFOUT.
V
OUT
=
FF
0 6
, may be used. Great care should be taken to
FB
.
Figure 14. Setting Output Voltage
line away from noise sources, such as the
V
•

 
LTC3829
1
+
R
R
V
FB
IN(MAX)
B
A

 
V
. When adjusting the gate
OUT
R
R
3829 F14
B
B
A
, needs to be 100 times
B
C
, should connect
FF
3829f