Datasheet LTC3812-5 (Analog Devices) - 8

LTC3812-5
TYPICAL PERFORMANCE CHARACTERISTICS RUN/SS Pull-Up Current Shutdown Threshold vs Temperature vs Temperature
3 2.2 RUN/SS = 0V 2.0 A) 1.8 μ 2 1.6 1.4 1.2 1 SS/TRACK CURRENT ( 1.0 SHUTDOWN THRESHOLD (V) 0.8 0 0.6 –50 –25 0 25 50 75 100 125 –50 –25 0 25 50 75 100 125 TEMPERATURE (°C) TEMPERATURE (°C) 38125 G27 38125 G28
PIN FUNCTIONS ION (Pin 1):
On-Time Current Input. Tie a resistor from VIN
ITH (Pin 5):
Error Amplifi er Compensation Point and Cur- to this pin to set the one-shot timer current and thereby rent Control Threshold. The current comparator threshold set the switching frequency. increases with control voltage. The voltage ranges from 0V to 2.6V with 1.2V corresponding to zero sense voltage
VRNG (Pin 2):
Sense Voltage Limit Set. The voltage at this (zero current). pin sets the nominal sense voltage at maximum output current and can be set from 0.5V to 2V by a resistive
VFB (Pin 6):
Feedback Input. Connect VFB through a resistor divider from INTVCC. The nominal sense voltage defaults divider network to VOUT to set the output voltage. to 95mV when this pin is tied to ground, and 215mV when
RUN/SS (Pin 7):
RUN/Soft-Start Input. For soft-start, a tied to INTVCC. capacitor to ground at this pin sets the ramp rate of the
PGOOD (Pin 3):
Power Good Output. Open-drain logic output voltage (approximately 0.6s/μF). Pulling this pin output that is pulled to ground when the output voltage below 1.5V will shut down the LTC3812-5, turn off both of is not between ±10% of the regulation point. The output the external MOSFET switches and reduce the quiescent voltage must be out of regulation for at least 120μs before supply current to 224μA. the power good output is pulled to ground.
SGND (Pin 8):
Signal Ground. All small-signal components
FCB (Pin 4):
Pulse-Skipping Mode Enable Pin. This pin should connect to this ground and eventually connect to provides pulse-skipping mode enable/disable control. PGND at one point. Pulling this pin below 0.8V disables pulse-skipping mode
NDRV (Pin 9):
Drive Output for External Pass Device of operation and forces continuous operation. Pulling this pin the Linear Regulator for INTV above 0.8V enables pulse-skipping mode operation. This CC. Connect to the gate of an external NMOS pass device and a pull-up resistor to pin can also be connected to a feedback resistor divider the input voltage V from a secondary winding on the inductor to regulate a IN. second output voltage. 38125fc 8