LTC1709-8_1 Datasheet, PDF (8/28 Pages) Linear Technology – 2-Phase, 5-Bit VID,Current Mode, High Efficiency,Synchronous Step-Down Switching Regulators

LTC1709-8/LTC1709-9
PI FU CTIO S
PLLIN (Pin 6): External Synchronization Input to Phase
Detector. This pin is internally terminated to SGND with
50kΩ. The phase-locked loop will force the rising top gate
signal of controller 1 to be synchronized with the rising
edge of the PLLIN signal.
NC (Pins 7, 36): Do not connect.
I_TH (Pin 8): Error Amplifier Output and Switching Regula-
tor Compensation Point. Both current comparator’s thresh-
olds increase with this control voltage. The normal voltage
range of this pin is from 0V to 2.4V
SGND (Pin 9): Signal Ground. This pin is common to both
controllers. Route separately to the PGND pin.
V_DIFFOUT (Pin 10): Output of a Differential Amplifier. This
pin provides true remote output voltage sensing. V_DIFFOUT
normally drives an external resistive divider that sets the
output voltage.
V_OS–, V_OS+ (Pins 11, 12): Inputs to an Operational Ampli-
fier. Internal precision resistors capable of being elec-
tronically switched in or out can configure it as a differential
amplifier or an uncommitted op amp.
ATTENOUT (Pin 15): Voltage Feedback Signal Resistively
Divided According to the VID Programming Code.
ATTENIN (Pin 16): The Input to the VID Controlled Resis-
tive Divider.
VID0–VID4 (Pins 17,18, 19, 20, 21): VID Control Logic
Input Pins.
V_BIAS (Pin 22): Supply Pin for the VID Control Circuit.
PGOOD (Pin 23): Open-Drain Logic Output. PGOOD is
pulled to ground when the voltage on the EAIN pin is not
within ±7.5% of its set point.
TG2, TG1 (Pins 24, 35): High Current Gate Drives for Top
N-Channel MOSFETS. These are the outputs of floating
drivers with a voltage swing equal to INTV_CC superim-
posed on the switch node voltage SW.
SW2, SW1 (Pins 25, 34): Switch Node Connections to
Inductors. Voltage swing at these pins is from a Schottky
diode (external) voltage drop below ground to V_IN.
BOOST2, BOOST1 (Pins 26, 33): Bootstrapped Supplies
to the Topside Floating Drivers. External capacitors are
connected between the BOOST and SW pins, and Schottky
diodes are connected between the BOOST and INTV_CC
pins.
BG2, BG1 (Pins 27, 31): High Current Gate Drives for
Bottom N-Channel MOSFETS. Voltage swing at these pins
is from ground to INTV_CC.
PGND (Pin 28): Driver Power Ground. Connect to sources
of bottom N-channel MOSFETS and the (–) terminals of
C_IN.
INTV_CC (Pin 29): Output of the Internal 5V Linear Low
Dropout Regulator and the EXTV_CC Switch. The driver and
control circuits are powered from this voltage source.
Decouple to power ground with a 1µF ceramic capacitor
placed directly adjacent to the IC and minimum of 4.7µF
additional tantalum or other low ESR capacitor.
EXTV_CC (Pin 30): External Power Input to an Internal
Switch. This switch closes and supplies INTV_CC, bypass-
ing the internal low dropout regulator whenever EXTV_CC is
higher than 4.7V. See EXTV_CC Connection in the Applica-
tions Information section. Do not exceed 7V on this pin
and ensure V_EXTVCC ≤ V_IN.
V_IN (Pin 32): Main Supply Pin. Should be closely de-
coupled to the IC’s signal ground pin.
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