LTC3829EFE#PBF Linear Technology, LTC3829EFE#PBF Datasheet - Page 25

• 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: -

applicaTions inForMaTion
The emergence of very low ESR capacitors in small, surface
mount packages makes very small physical implementa-
tions possible. The ability to externally compensate the
switching regulator loop using the I
wider selection of output capacitor types. The impedance
characteristic of each capacitor type is significantly differ-
ent than an ideal capacitor and therefore requires accurate
modeling or bench evaluation during design. Manufacturers
such as Nichicon, Nippon Chemi-Con and Sanyo should be
considered for high performance through-hole capacitors.
The OS-CON semiconductor dielectric capacitors available
from Sanyo and the Panasonic SP surface mount types
have a good (ESR)(size) product.
Once the ESR requirement for C
RMS current rating generally far exceeds the I
requirement. Ceramic capacitors from AVX, Taiyo Yuden,
Murata and Tokin offer high capacitance value and very
low ESR, especially applicable for low output voltage
applications.
In surface mount applications, multiple capacitors may
have to be paralleled to meet the ESR or RMS current
handling requirements of the application. Aluminum
electrolytic and dry tantalum capacitors are both available
in surface mount configurations. New special polymer
surface mount capacitors offer very low ESR also but
have much lower capacitive density per unit volume. In
the case of tantalum, it is critical that the capacitors are
surge tested for use in switching power supplies. Several
excellent choices are the AVX TPS, AVX TPSV, the KEMET
T510 series of surface mount tantalums or the Panasonic
SP series of surface mount special polymer capacitors
available in case heights ranging from 2mm to 4mm. Other
capacitor types include Sanyo POSCAP , Sanyo OS-CON,
Nichicon PL series and Sprague 595D series. Consult the
manufacturers for other specific recommendations.
OUT
TH
has been met, the
pin allows a much
RIPPLE(P-P)
Differential Amplifier
The LTC3829 has a true remote voltage sense capability.
The sensing connections should be returned from the
load, back to the differential amplifier’s inputs through a
common, tightly coupled pair of PC traces. The differential
amplifier rejects common mode signals capacitively or
inductively radiated into the feedback PC traces as well as
ground loop disturbances. The differential amplifier output
signal is divided by a pair of resistors and is compared
with the internal, precision 0.6V voltage reference by the
error amplifier.
Active Voltage Positioning (AVP)
In an application, the AVP scheme modifies the regu-
lated output voltage depending its current loading. AVP
can improve overall transient response and save power
consumption.
The LTC3829 senses inductor current information through
monitoring voltage drops on the sense resistor R
DCR sensing network of all three channels. The voltage
drops are added together and applied as V
the AVP and DIFFP pins, which are connected through
resistor R
and added to output voltage as the compensation for the
load voltage drop.
Let:
then:
∆V = V
∆V = V
∆V = V
∆
V
DIFFP VOUT
SENSE1
SENSE2
SENSE3
PRE-AVP
,
+
+
+
=
. Then V
– V
– V
– V
3
•
SENSE1
SENSE2
SENSE3
∆
V

 
PRE-AVP
R
–
–
–
PRE-AVP
R
AVP
is scaled through R

 
LTC3829
PRE-AVP
between
SENSE

AVP
3829f
or