Datasheet LT3791-1 (Analog Devices) - 10

LT3791-1
pin FuncTions BST2 (Pin 22):
Bootstrapped Driver Supply. The BST2 pin voltage is less than 0.3V, the part runs in discontinuous swings from a diode voltage below INTVCC up to a diode conduction mode and does not allow the inductor current voltage below VOUT + INTVCC. to flow backward. This pin is only meant to block inductor reverse current, and should only be pulled low when the
NC (Pin 23):
No Connect Pin. Leave this pin floating. output current is low. This pin must be either connected to
TG2 (Pin 24):
Top Gate Drive. Drives the top N-channel INTVCC (pin 13) for continuous conduction mode across MOSFET with a voltage equal to INTVCC superimposed on all loads, or it must be connected to the C/10 (pin 4) with the switch node voltage SW2. a pull-up resistor to INTVCC for continuous conduction
ISP (Pin 25):
Connection Point for the Positive Terminal mode at heavy load and for discontinuous conduction of the Output Current Feedback Resistor. mode at light load.
ISN (Pin 26):
Connection Point for the Negative Terminal
CLKOUT (Pin 33):
Clock Output Pin. A 180° out-of-phase of the Output Current Feedback Resistor. clock is provided at the oscillator frequency to allow for par- alleling two devices for extending output power capability.
SNSP (Pin 27):
The Positive Input to the Current Sense Comparator. The V
SYNC (Pin 34):
External Synchronization Input Pin. This C pin voltage and controlled offsets between the SNSP and SNSN pins, in conjunction with a pin is internally terminated to GND with a 90k resistor. resistor, set the current trip threshold. The internal buck clock is synchronized to the rising edge of the SYNC signal while the internal boost clock is 180°
SNSN (Pin 28):
The Negative Input to the Current Sense phase shifted. Comparator.
RT (Pin 35):
Frequency Set Pin. Place a resistor to GND
TEST1 (Pin 29):
This pin is used for testing purposes only to set the internal frequency. The range of oscillation is and must be connected to SGND for the part to operate 200kHz to 700kHz. properly.
VC (Pin 36):
Current Control Threshold and Error Amplifier
SGND (Pin 30, Exposed Pad Pin 39):
Signal Ground. Compensation Point. The current comparator threshold All small-signal components and compensation should increases with this control voltage. The voltage ranges connect to this ground, which should be connected to from 0.7V to 1.9V. PGND at a single point. Solder the exposed pad directly to the ground plane.
FB (Pin 37):
Voltage Loop Feedback Pin. FB is intended for constant-voltage regulation. The internal transconductance
PWMOUT (Pin 31):
Buffered Version of PWM Signal for amplifier with output VC will regulate FB to 1.2V (typical) Driving Output Load Disconnect N-Channel MOSFET. The through the DC/DC converter. If the FB input is regulat- PWMOUT pin is driven from INTVCC. Use of a MOSFET ing the loop and V(ISP-ISN) < 10mV, the C/10 pull-down with a gate cutoff voltage higher than 1V is recommended. is asserted. If the FB pin is less than 400mV, the SHORT
CCM (Pin 32):
Continuous Conduction Mode Pin. When pull-down is asserted. the pin voltage is higher than 1.5V, the part runs in fixed
OVLO (Pin 38):
Overvoltage Input Pin. This pin is used for frequency forced continuous conduction mode and al- OVLO, if OVLO > 3V then SS is pulled low, the part stops lows the inductor current to flow negative. When the pin switching and resets. Do not leave this pin open. 37911fb 10 For more information www.linear.com/LT3791-1 Document Outline Features Applications Description Typical Application Absolute Maximum Ratings Pin Configuration Electrical Characteristics Typical Performance Characteristics Pin Functions Block Diagram Operation Applications Information Typical Applications Typical Application Related Parts