LTC3857IUH#PBF Linear Technology, LTC3857IUH#PBF Datasheet - Page 28

• Manufacturer Part Number: LTC3857IUH#PBF
• Description: IC CTRLR STP-DN SYNC DUAL 32QFN
• Manufacturer: Linear Technology
• Series: PolyPhase®r
• Type: Step-Down (Buck)r

Specifications of LTC3857IUH#PBF

• Internal Switch(s): No
• Synchronous Rectifier: Yes
• Number Of Outputs: 2
• Voltage - Output: 0.8 ~ 24 V
• Frequency - Switching: 50kHz ~ 900kHz
• Voltage - Input: 4 ~ 38 V
• Operating Temperature: -40°C ~ 125°C
• Mounting Type: Surface Mount
• Package / Case: 32-QFN
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Current - Output: -
• Power - Output: -

APPLICATIONS INFORMATION
LTC3857
28
4. Are the SENSE
5. Is the INTV
minimum PC trace spacing? The filter capacitor between
SENSE
to the IC. Ensure accurate current sensing with Kelvin
connections at the SENSE resistor.
to the IC, between the INTV
pins? This capacitor carries the MOSFET drivers’ cur-
rent peaks. An additional 1μF ceramic capacitor placed
immediately next to the INTV
improve noise performance substantially.
+
and SENSE
R
IN
CC
V
IN
–
decoupling capacitor connected close
C
and SENSE
IN
BOLD LINES INDICATE
HIGH SWITCHING
CURRENT. KEEP LINES
TO A MINIMUM LENGTH.
–
should be as close as possible
+
CC
leads routed together with
CC
and PGND pins can help
and the power ground
Figure 12. Branch Current Waveforms
SW1
SW2
D1
D2
6. Keep the switching nodes (SW1, SW2), top gate nodes
7. Use a modified star ground technique: a low impedance,
L1
L2
(TG1, TG2), and boost nodes (BOOST1, BOOST2) away
from sensitive small-signal nodes, especially from
the opposites channel’s voltage and current sensing
feedback pins. All of these nodes have very large and
fast moving signals and therefore should be kept on
the output side of the LTC3857 and occupy minimum
PC trace area.
large copper area central grounding point on the same
side of the PC board as the input and output capacitors
with tie-ins for the bottom of the INTV
capacitor, the bottom of the voltage feedback resistive
divider and the SGND pin of the IC.
R
R
SENSE1
SENSE2
C
C
OUT1
OUT2
V
V
OUT1
OUT2
3857 F12
R
R
L1
L2
CC
decoupling
3857fc