LTC3709 Linear Technology, LTC3709 Datasheet - Page 11

• Manufacturer Part Number: LTC3709
• Description: No RSENSE Synchronous DC/DC Controller
• Manufacturer: Linear Technology

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OPERATIO
DRV
Power for the top and bottom MOSFET drivers and most
of the internal controller circuitry is derived from the
DRV
floating bootstrap capacitor C
recharged from DRV
ode D
Differential Amplifier
This amplifier provides true differential output voltage
sensing. Sensing both V
tion in high current applications and/or applications hav-
ing electrical interconnection losses. This sensing also
isolates the physical power ground from the physical
signal ground, preventing the possibility of troublesome
“ground loops” on the PC layout and preventing voltage
errors caused by board-to-board interconnects.
CC
CC
B
when the top MOSFET is turned off.
pin. The top MOSFET driver is powered from a
U
CC
(Refer to Functional Diagram)
through an external Schottky di-
OUT
+
B
and V
. This capacitor is normally
OUT
–
benefits regula-
Dual Phase Operation
An internal phase-lock loop (PLL1) ensures that channel
2 operates exactly at the same frequency as channel 1 and
is also phase shifted by 180°, enabling the LTC3709 to
operate optimally as a dual phase controller. The loop filter
connected to the INTLPF pin provides stability to the PLL.
For external clock synchronization, a second PLL (PLL2)
is incorporated into the LTC3709. PLL2 will adjust the on-
time of channel 1 until its frequency is the same as the
external clock. When locked, the PLL2 aligns the turn on
of the top MOSFET of channel 1 to the rising edge of the
external clock. Compensation for PLL2 is through the
EXTLPF pin.
Second Channel Shutdown During Light Loads
When FCB is tied to V
In this mode, no reverse current is allowed. The second
channel is off when I
efficiency. When FCB is tied to ground, forced continuous
mode is selected, both channels are on and reversed
current is allowed.
CC
TH
, discontinuous mode is selected.
is less than 0.8V for better
LTC3709
11
3709f