Datasheet LT3758, LT3758A (Analog Devices) - 8

LT3758/LT3758A
PIN FUNCTIONS VC (Pin 1):
Error Amplifier Compensation Pin. Used to
GATE (Pin 7):
N-Channel MOSFET Gate Driver Output. stabilize the voltage loop with an external RC network. Switches between INTVCC and GND. Driven to GND when
FBX (Pin 2):
Positive and Negative Feedback Pin. IC is shut down, during thermal lockout or when INTVCC Receives the feedback voltage from the external resistor is above or below the overvoltage or UV thresholds, divider across the output. Also modulates the switching respectively. frequency during start-up and fault conditions when FBX
INTVCC (Pin 8):
Regulated Supply for Internal Loads and is close to GND. Gate Driver. Supplied from VIN and regulated to 7.2V (typi-
SS (Pin 3):
Soft-Start Pin. This pin modulates compensa- cal). INTVCC must be bypassed with a minimum of 4.7µF tion pin voltage (V capacitor placed close to pin. INTVCC can be connected C) clamp. The soft-start interval is set with an external capacitor. The pin has a 10µA (typical) directly to VIN, if VIN is less than 17.5V. INTVCC can also pull-up current source to an internal 2.5V rail. The soft- be connected to a power supply whose voltage is higher start pin is reset to GND by an undervoltage condition than 7.5V, and lower than VIN, provided that supply does at SHDN/UVLO, an INTV not exceed 17.5V. CC undervoltage or overvoltage condition or an internal thermal lockout.
SHDN/UVLO (Pin 9):
Shutdown and Undervoltage Detect
RT (Pin 4):
Switching Frequency Adjustment Pin. Set the Pin. An accurate 1.22V (nominal) falling threshold with frequency using a resistor to GND. Do not leave this pin externally programmable hysteresis detects when power open. is okay to enable switching. Rising hysteresis is generated by the external resistor divider and an accurate internal
SYNC (Pin 5):
Frequency Synchronization Pin. Used to 2µA pull-down current. An undervoltage condition resets synchronize the switching frequency to an outside clock. sort-start. Tie to 0.4V, or less, to disable the device and If this feature is used, an RT resistor should be chosen reduce VIN quiescent current below 1µA. to program a switching frequency 20% slower than the SYNC pulse frequency. Tie the SYNC pin to GND if this
VIN (Pin 10):
Input Supply Pin. Must be locally bypassed feature is not used. SYNC is bypassed when FBX is close with a 0.22µF, or larger, capacitor placed close to the pin. to GND.
Exposed Pad (Pin 11):
Ground. This pin also serves as
SENSE (Pin 6):
The Current Sense Input for the Control the negative terminal of the current sense resistor. The Loop. Kelvin connect this pin to the positive terminal of exposed pad must be soldered directly to the local ground the switch current sense resistor in the source of the plane. NFET. The negative terminal of the current sense resis- tor should be connected to GND plane close to the IC. Rev F 8 For more information www.analog.com Document Outline Features Applications Description Typical Application Absolute Maximum Ratings Pin Configuration Order Information Electrical Characteristics Typical Performance Characteristics Pin Functions Block Diagram Applications Information Typical Applications Package Description Revision History Typical Applications Related Parts Typical Applications Features Applications Typical Application Description Absolute Maximum Ratings Pin Configuration Order Information Electrical Characteristics Typical Performance Characteristics Pin Functions Block Diagram Applications Information Typical Applications Package Description Revision History Typical Application Related Parts