LTC3716EG Linear Technology, LTC3716EG Datasheet - Page 25

• Manufacturer Part Number: LTC3716EG
• Description: IC SW REG STP-DN 5BIT SYNC36SSOP
• Manufacturer: Linear Technology
• Type: Step-Down (Buck)r

Specifications of LTC3716EG

• Internal Switch(s): No
• Synchronous Rectifier: Yes
• Number Of Outputs: 1
• Voltage - Output: 0.6 ~ 1.75 V
• Current - Output: 35mA
• Frequency - Switching: 120kHz ~ 310kHz
• Voltage - Input: 4 ~ 36 V
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 36-SSOP
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant
• Power - Output: -

APPLICATIO S I FOR ATIO
3) Are the SENSE
minimum PC trace spacing? The filter capacitors between
SENSE
possible to the LTC3716. Ensure accurate current sensing
with Kelvin connections at the current sense resistor. See
Figure 10.
4) Does the (+) plate of C
topside MOSFETs as closely as possible? This capacitor
provides the AC current to the MOSFETs. Keep the input
current path formed by the input capacitor, top and bottom
MOSFETs, and the Schottky diode on the same side of the
PC board in a tight loop to minimize conducted and
radiated EMI.
5) Is the INTV
nected closely between INTV
capacitor carries the MOSFET driver peak currents. A
small value is recommended to allow placement immedi-
ately adjacent to the IC.
+
and SENSE
R
IN
CC
V
IN
–
1 F ceramic decoupling capacitor con-
C
and SENSE
IN
BOLD LINES INDICATE
HIGH, SWITCHING
CURRENT LINES.
KEEP LINES TO A
MINIMUM LENGTH.
U
+
–
Figure 11. Instantaneous Current Path Flow in a Multiple Phase Switching Regulator
pin pairs should be as close as
IN
U
connect to the drains of the
CC
+
leads routed together with
and the PGND pin? This
W
SW1
SW2
U
D1
D2
L1
L2
6) Keep the switching nodes, SW1 (SW2), away from
sensitive small-signal nodes. Ideally the switch nodes
should be placed at the furthest point from the
LTC3716.
7) Use a low impedance source such as a logic gate to drive
the PLLIN pin and keep the lead as short as possible.
The diagram in Figure 11 illustrates all branch currents in
a 2-phase switching regulator. It becomes very clear after
studying the current waveforms why it is critical to keep
the high-switching-current paths to a small physical size.
High electric and magnetic fields will radiate from these
“loops” just as radio stations transmit signals. The output
capacitor ground should return to the negative terminal of
the input capacitor and not share a common ground path
with any switched current paths. The left half of the circuit
gives rise to the “noise” generated by a switching regula-
tor. The ground terminations of the sychronous MOSFETs
and Schottky diodes should return to the negative plate(s)
R
R
SENSE1
SENSE2
3716 F11
+
C
V
OUT
OUT
LTC3716
R
L
25