Datasheet LTC7801 (Analog Devices) - 10

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PIN FUNCTIONS (QFN/TSSOP) DRVCC (Pin 15/Pin 17):
Output of the Internal or External
INTVCC (Pin 20/Pin 22):
Output of the Internal 5V Low Low Dropout Regulators. The gate drivers are powered Dropout Regulator. Many of the low voltage analog and from this voltage source. The DRVCC voltage is set by digital circuits are powered from this voltage source. A the DRVSET pin. Must be decoupled to ground with a low ESR 0.1µF ceramic bypass capacitor should be con- minimum of 4.7µF ceramic or other low ESR capacitor, nected between INTVCC and GND, as close as possible to as close as possible to the IC. Do not use the DRVCC pin the LTC7801. for any other purpose.
OVLO (Pin 21/Pin 23):
Overvoltage Lockout Input. A
NDRV (Pin 16/Pin 18):
Drive Output for External Pass voltage on this pin above 1.2V disables switching of Device of the NDRV LDO Linear Regulator for DRVCC. the controller. The DRVCC and INTVCC supplies maintain Connect this pin to the gate of an external NMOS pass regulation during an OVLO event. Exceeding the OVLO device. An internal charge pump allows NDRV to regulate threshold triggers a soft-start reset. If the OVLO function above VIN for low dropout performance. To disable this is not used, connect this pin to GND. external NDRV LDO, tie NDRV to DRVCC.
SENSE+ (Pin 22/Pin 24):
The (+) Input to the Differential
VIN (Pin 17/Pin 19):
Main Supply Pin. A bypass capacitor Current Comparator. The ITH pin voltage and controlled should be tied between this pin and the GND pins. offsets between the SENSE– and SENSE+ pins in conjunc-
EXTV
tion with RSENSE set the current trip threshold.
CC (Pin 18/Pin 20):
External Power Input to an Internal LDO linear regulator Connected to DRVCC. This
SENSE– (Pin 23/Pin 1):
The (–) Input to the Differential LDO supplies DRVCC power from EXTVCC, bypassing the Current Comparator. When SENSE– is greater than INTVCC, internal LDO powered from VIN or the external NDRV LDO the SENSE– pin supplies power to the current comparator. whenever EXTVCC is higher than its switchover threshold
SS (Pin 24/Pin 2):
Soft-Start Input. The LTC7801 regu- (4.7V or 7.7V depending on the DRVUV pin). See DRVCC lates the V Regulators in the Applications Information section. Do FB voltage to the smaller of 0.8V or the voltage on the SS pin. An internal 10μA pull-up current source is not exceed 14V on this pin. Do not connect EXTVCC to a connected to this pin. A capacitor to ground at this pin voltage greater than VIN. If not used, connect to GND and sets the ramp time to final regulated output voltage. The place a 330k or smaller resistor between INTVCC and SS. SS pin is also used for the Regulator Shutdown (REGSD)
RUN (Pin 19/Pin 21):
Run Control Input. Forcing this pin feature. A 5μA/1μA pull-down current can be connected below 1.12V shuts down the controller. Forcing this pin on SS depending on the state of the EXTVCC LDO and the below 0.7V shuts down the entire LTC7801, reducing qui- voltage on SS. See Regulator Shutdown in the Operation escent current to approximately 10µA. This pin can be section for more information. To defeat the REGSD fea- tied to VIN for always-on operation. Do not float this pin. ture, place a 330k or smaller resistor between INTVCC and SS. See Soft-Start Pin in the Applications Information section for more information on defeating REGSD. Rev. A 10 For more information www.analog.com Document Outline Features Applications Typical Application Description Absolute Maximum Ratings Pin Configuration Order Information Electrical Characteristics Typical Performance Characteristics Pin Functions Functional Diagram Operation Applications Information Typical Applications Package Description Revision History Typical Application Related Parts