LT3003 datasheet(6/20 Pages) LINER

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LT3517

3517ff

PIN FUNCTIONS

SW: Switch Pin. Minimize trace at this pin to reduce EMI.

VIN: Input Supply Pin. Must be locally bypassed.

SHDN: Shutdown Pin. Tie to 1.5V or higher to enable

device or 0.4V or less to disable device.

VREF: Reference Output Pin. This pin can supply up to

100μA.

RT: Switching Frequency Adjustment Pin. Set switching

frequency using a resistor to GND (see Typical Performance

Characteristics for values). For SYNC function, choose

the resistor to program a frequency 20% slower than the

SYNC pulse frequency. Do not leave this pin open.

SYNC: Frequency Synchronization Pin. Tie an external

clock signal here. RT resistor should be chosen to pro-

gram a switching frequency 20% slower than SYNC pulse

frequency. Synchronization (power switch turn-on) occurs

a fixed delay after the rising edge of SYNC. Tie the SYNC

pin to ground if this feature is not used.

SS: Soft-Start Pin. Place a soft-start capacitor here. Leave

the pin open if not in use.

PWM: Pulse Width Modulated Input Pin. Signal low turns

off channel, disables the main switch and makes the TG

pin high. Tie the PWM pin to VREF pin or SHDN pin if not

used. There is an equivalent 50k resistor from PWM pin

to ground internally.

CTRL: LED Current Adjustment Pin. Sets voltage across

sense resistor between ISP and ISN. Connect directly to

VREF for full-scale threshold of 100mV, or use signal values

between GND and 1V to modulate LED current. Tie the CTRL

pin to the VREF pin if not used.

VC: gm Error Amplifier Output Pin. Stabilize the loop with

an RC network or compensating C.

FB: Voltage Loop Feedback Pin. Works as overvoltage

protection for LED drivers. If FB is higher than 1V, the

main switch is turned off.

TGEN: Top Gate Enable Input Pin. Tie to 1.5V or higher

to enable the PMOS driver function. Tie the TGEN pin to

ground if TG function is not used. There is an equivalent

40k resistor from TGEN pin to ground internally.

ISN: Current Sense (–) Pin. The inverting input to the

current sense amplifier.

ISP: Current Sense (+) Pin. The noninverting input to the

current sense amplifier. Also serves as positive rail for

TG pin driver.

TG: Top Gate Driver Output. An inverted PWM sig-

nal drives series PMOS device between VISP and

(VISP – 7V). An internal 7V clamp protects the PMOS gate.

Leave TG unconnected if not used.

GND: Exposed Pad (QFN Package). Solder paddle directly

to ground plane.

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