Datasheet LTC3769 (Analog Devices) - 9

LTC3769
PIN FUNCTIONS (QFN/TSSOP)
input determines how the LTC3769 operates at light loads.
OVMODE (Pin 17/Pin 12):
Overvoltage Mode Selection Pulling this pin to ground selects Burst Mode operation. Input. This pin is used to select how the LTC3769 operates An internal 100k resistor to ground also invokes Burst when the output feedback voltage (VFB) is overvoltage Mode operation when the pin is floated. Tying this pin (>110% of its normal regulated point of 1.2V). It is also to INTVCC forces continuous inductor current operation. used to determine the light-load mode of operation when Tying this pin to a voltage greater than 1.2V and less than the LTC3769 is synchronized to an external clock through INTVCC – 1.3V selects pulse-skipping operation. This can the PLLIN/MODE pin. be done by adding a 100k resistor between the PLLIN/ When OVMODE is tied to ground, overvoltage protection MODE pin and INTVCC. is enabled and the top MOSFET gate (TG) is turned on
RUN (Pin 11/Pin 6):
Run Control Input. Forcing this pin continuously until the overvoltage condition is cleared. below 1.28V shuts down the controller. Forcing this pin When OVMODE is grounded, the LTC3769 operates in below 0.7V shuts down the entire LTC3769, reducing forced continuous mode when synchronized. There is an quiescent current to approximately 4µA. An external internal weak pull-down resistor that pulls the OVMODE resistor divider connected to VIN can set the threshold pin to ground when it is left floating. for converter operation. Once running, a 4.5µA current is When OVMODE is tied to INTV sourced from the RUN pin allowing the user to program CC, overvoltage protection is disabled and TG is not forced on during an overvolt- hysteresis using the resistor values. age event. Instead, the state of TG is determined by the
SS (Pin 12/Pin 7):
Output Soft-Start Input. A capacitor to mode of operation selected by the PLLIN/MODE pin and ground at this pin sets the ramp rate of the output voltage the inductor current. See the Operation section for more during start-up. details. When OVMODE is tied to INTVCC, the LTC3769
SENSE– (Pin 13/Pin 8):
Negative Current Sense Comparator operates in pulse-skipping mode when synchronized. Input. The (–) input to the current comparator is normally
SW (Pin 18/Pin 13):
Switch Node. Connect to the source connected to the negative terminal of a current sense of the synchronous N-channel MOSFET, the drain of the resistor connected in series with the inductor. main N-channel MOSFET and the inductor.
SENSE+ (Pin 14/Pin 9):
Positive Current Sense Comparator
TG (Pin 19/Pin 14):
Top Gate. Connect to the gate of the Input. The (+) input to the current comparator is normally synchronous N-channel MOSFET. connected to the positive terminal of a current sense resis-
BOOST (Pin 20/Pin 15):
Floating power supply for the tor. The current sense resistor is normally placed at the synchronous N-channel MOSFET. Bypass to SW with a input of the boost controller in series with the inductor. capacitor and supply with a Schottky diode connected This pin also supplies power to the current comparator. to INTV The common mode voltage range on SENSE+ and SENSE– CC. pins is 2.3V to 60V (65V abs max).
BG (Pin 21/Pin 16):
Bottom Gate. Connect to the gate of the main N-channel MOSFET.
VFB (Pin 15/Pin 10):
Error Amplifier Feedback Input. This pin receives the remotely sensed feedback voltage from
EXTVCC (Pin 23/Pin 18):
External Power Input to an internal an external resistive divider connected across the output. LDO Connected to INTVCC. This LDO supplies INTVCC power, bypassing the internal LDO powered from V
ITH (Pin 16/Pin 11):
Current Control Threshold and Error BIAS whenever EXTV Amplifier Compensation Point. The voltage on this pin sets CC is higher than 4.7V. See EXTVCC Connection in the Applications Information section. Do not float or exceed the current trip threshold. 14V on this pin. Connect to ground if not used. 3769fa For more information www.linear.com/LTC3769 9 Document Outline Features Applications Description Typical Application Absolute Maximum Ratings Pin Configuration Order Information Electrical Characteristics Typical Performance Characteristics Pin Functions Block Diagram Operation Applications Information Typical Applications Revision History Typical Application Related Parts