RT8100 Datasheet, PDF (4/18 Pages) Richtek Technology Corporation – Synchronous buck PWM DC/DC with Dual Voltage Control Mode

RT8100
Preliminary
Functional Pin Description
5VSB(Pin 1), 12VCC (Pin 16)
The 5VSB pin is the external standby 5V power. The 12VCC
pin is the external 12V power.
RT (Pin 2)
Timing Resistor. Connect a resistor from RT to GND to set
the clock frequency. The free running frequency is 200kHz.
I_IND (Pin 3)
Current indicating pin. This pin uses voltage level to indicate
the current of inductor. Connect this pin with a resistor to
ground to set the voltage.
I__IND = 4 x I_X
I_X : Internal GM sensed current, please refer to the
Application Information.
RR (Pin 4)
Ramp resistor. This pin is used to set the ramp voltage.
Connecting a resistor from this pin to the converter input
power sets the ramping slope of the control loop of the
converter. Since it is connected to the converter input
power, the ramp slope is input-feed-forwarded. As V_IN >
1.8V, RR pin is enabled for ramp setting.
CSN (Pin 5)
Current Sense Negative Input. This pin is negative input
node of the current sense amplifier used for DCR current
sensing. Connect this pin with a resistor to the output
node.
CSP (Pin 6)
Current Sense Positive Input. This pin is positive input
nodes of the current sense amplifier used for DCR current
sensing. Connect this pin to the junction of the filter resistor
and capacitor.
COMP (Pin 7)
Compensation Pin. This pin is the output node of the error
amplifier.
FB (Pin 8)
Feedback Pin. This pin is negative input pin of the error
amplifier.
PI (Pin 9)
External reference voltage pin. This pin sets the voltage of
FB pin when close loop.
Stand_Alone : Pull high to 5VSB
Tracking : Connect to external reference voltage. The PI
pin will sink 4mA for 15μs when the OCP function acts.
SS (Pin 10)
Soft-start Pin. This pin provides soft-start function for its
controller. The COMP voltage of the converter follows the
ramping voltage on the SS pin.
PVCC (Pin 11)
Driver Power.
LGATE (Pin 12)
Lower Gate Drive. This pin drives the gate of the lowside
MOSFET.
PHASE (Pin 13)
This pin is return node of the high-side driver. Connect this
pin to high-side MOSFET source together with the low-
side MOSFET drain and the inductor.
UGATE (Pin 14)
Upper Gate Drive. This pin drives the gate of the highside
MOSFET.
BOOT (Pin 15)
Bootstrap Power Pin. This pin powers the high-side
MOSFET driver. Connect this pin to the junction of the
bootstrap capacitor.
GND [Exposed Pad (17)]
The exposed pad must be soldered to a large PCB and
connected to GND for maximum power dissipation.
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DS8100-03 August 2007