Datasheet LT3596 (Analog Devices) - 8

LT3596 pin FuncTions
FB (Pin 2):
Feedback Pin. This pin is regulated to the
FAULT (25):
Fault Detection Pin. Open-collector pin used internal bandgap voltage. The maximum buck output to report open LED faults. FAULT must be externally pulled voltage is set by connecting this pin to a resistor divider to a positive supply. from VOUT .
SYNC (Pin 27):
External Clock Synchronization Pin. When
EN/UVLO (Pin 4):
Enable and Undervoltage Lockout Pin. an external clock drives this pin, the buck regulator is Accurate 1.5V falling threshold. UVLO threshold is pro- synchronized to that frequency. Frequency programmed grammed by using a resistor divider from VIN. by the RT pin resistor must be at least 20% slower than
TSET (Pin 6):
Thermal Regulation Pin. Programs the the SYNC pin clock frequency. LT3596 junction temperature at which LED current begins
PWM1, PWM2, PWM3 (Pins 30, 29, 28):
PWM Dimming to derate. Control Pin. When driven to a logic high, the LED1-3 current
V
sink is enabled. Channels can be individually disabled by
REF (Pin 7):
2V Reference Output Pin. This pin sources up to 200µA and is used to program TSET and CTRLM. tying PWM1-3 to ground. If PWM dimming is not desired then the pin should be connected to VREF .
GND (Pin 9/Exposed Pad Pin 53):
Ground Pin. This is the ground for both the IC and the switching converter.
CTRL1, CTRL2, CTRL3 (Pins 33, 32, 31):
Analog Dimming Exposed pad must be soldered to PCB ground. Control Pin. This pin is used to dim the LED current in an analog fashion. If the pin is tied to a voltage lower than
NC (Pins 11, 12, 18, 22, 23, 26, 34, 35, 39, 41, 43):
No 1.0V, it will linearly reduce the LED current. If unused the Connection Pins. Tie to ground if unused. pin must be connected to VREF .
CTRLM (Pin 13):
Master Control Pin. LED current derating
BIAS (37):
Supply Pin. This pin is the supply for an internal vs temperature is achievable for all channels if the voltage voltage regulator for analog and digital circuitry. BIAS must on CTRLM has a negative coefficient using an external be locally bypassed with a 4.7µF capacitor. NTC resistor divider from VREF .
DA (44):
Catch Diode Anode. This pin is used to provide
ISET1, ISET2, ISET3 (Pins 14, 15, 16):
LED Current Pro- frequency foldback in extreme situations. gramming Pin. Resistor to ground programs full-scale LED current.
BOOST (Pin 46):
Boost Capacitor Pin. This pin is used to provide a voltage above the input voltage when the switch
RT (Pin 17):
Switching Frequency Programming Pin. A is on. It supplies current to the switch driver. resistor to ground programs switching frequency between 200kHz and 1MHz. For the SYNC function, choose the
SW (Pin 48):
Switch Pin. Connect the inductor, catch diode resistor to program a frequency 20% slower than the and boost capacitor to this pin. SYNC pulse frequency.
VIN (Pins 50, 51):
Input Supply Pins. Pins are electrically
V
connected inside the package. VIN must be local y bypassed
OUT (Pin 19):
Buck Output. This is the buck regulator output voltage sense into the IC. with a 10µF capacitor to ground.
LED1, LED2, LED3 (Pins 20, 21, 24):
Constant-Current Sink Pin. These are three LED driver outputs, each contain- ing an open collector, constant current sink. All outputs are matched within ±1.5% and are individually programmed up to 100mA using an external resistor at the ISET1-3 pin. Outputs are rated to allow a maximum VOUT of 42V. Con- nect the cathode of the LED string to LED1-3. Connect the anode of the LED string to VOUT . 3596fa Document Outline Features Description Applications Typical Application Absolute Maximum Ratings Pin Configuration Order Information Electrical Characteristics Typical Performance Characteristics Pin Functions Block Diagram Operation Applications Information Package Description Revision History Typical Application Related Parts