Datasheet LTC7801 (Analog Devices) - 10

LTC7801
pin FuncTions (QFN/TSSOP) NDRV (Pin 16/Pin 18):
Drive Output for External Pass nected between INTVCC and GND, as close as possible to Device of the NDRV LDO Linear Regulator for DRVCC. the LTC7801. Connect this pin to the gate of an external NMOS pass
OVLO (Pin 21/Pin 23):
Overvoltage Lockout Input. A voltage device. An internal charge pump allows NDRV to regulate on this pin above 1.2V disables switching of the controller. above VIN for low dropout performance. To disable this The DRV external NDRV LDO, tie NDRV to DRV CC and INTVCC supplies maintain regulation during CC. an OVLO event. Exceeding the OVLO threshold triggers a
VIN (Pin 17/Pin 19):
Main Supply Pin. A bypass capacitor soft-start reset. If the OVLO function is not used, connect should be tied between this pin and the GND pins. this pin to GND.
EXTVCC (Pin 18/Pin 20):
External Power Input to an
SENSE+ (Pin 22/Pin 24):
The (+) Input to the Differential Internal LDO linear regulator Connected to DRVCC. This Current Comparator. The ITH pin voltage and controlled LDO supplies DRVCC power from EXTVCC, bypassing the offsets between the SENSE– and SENSE+ pins in conjunc- internal LDO powered from VIN or the external NDRV LDO tion with RSENSE set the current trip threshold. whenever EXTVCC is higher than its switchover threshold
SENSE– (Pin 23/Pin 1):
The (–) Input to the Differential (4.7V or 7.7V depending on the DRVUV pin). See DRVCC Current Comparator. When SENSE– is greater than INTV Regulators in the Applications Information section. Do CC, the SENSE– pin supplies power to the current comparator. not exceed 14V on this pin. Do not connect EXTVCC to a voltage greater than VIN. If not used, connect to GND and
SS (Pin 24/Pin 2):
Soft-Start Input. The LTC7801 regu- place a 330k or smaller resistor between INTVCC and SS. lates the VFB voltage to the smaller of 0.8V or the voltage on the SS pin. An internal 10μA pull-up current source is
RUN (Pin 19/Pin 21):
Run Control Input. Forcing this pin connected to this pin. A capacitor to ground at this pin below 1.12V shuts down the controller. Forcing this pin sets the ramp time to final regulated output voltage. The below 0.7V shuts down the entire LTC7801, reducing SS pin is also used for the Regulator Shutdown (REGSD) quiescent current to approximately 10µA. This pin can be feature. A 5μA/1μA pull-down current can be connected tied to VIN for always-on operation. Do not float this pin. on SS depending on the state of the EXTVCC LDO and the
INTVCC (Pin 20/Pin 22):
Output of the Internal 5V Low voltage on SS. See Regulator Shutdown in the Operation Dropout Regulator. Many of the low voltage analog and section for more information. To defeat the REGSD feature, digital circuits are powered from this voltage source. A place a 330k or smaller resistor between INTVCC and SS. low ESR 0.1µF ceramic bypass capacitor should be con- See Soft-Start Pin in the Applications Information section for more information on defeating REGSD. 7801f 10 For more information www.linear.com/LTC7801 Document Outline Features Description Applications Typical Application Absolute Maximum Ratings Pin Configuration Order Information Electrical Characteristics Typical Performance Characteristics Pin Functions Functional Diagram Operation Applications Information Typical Applications Package Description Typical Application Related Parts