lt3517 Linear Technology Corporation, lt3517 Datasheet - Page 6

• Manufacturer Part Number: lt3517
• Description: Full-featured Led Driver With 1.5a Switch Current
• Manufacturer: Linear Technology Corporation

LT3517
SW: Switch Pin. Minimize trace at this pin to reduce
EMI.
V
SHDN: Shutdown Pin. Tie to 1.5V or higher to enable
device or 0.4V or less to disable device.
V
100μA.
R
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. R
gram a switching frequency 20% slower than SYNC pulse
frequency. Synchronization (power switch turn-on) occurs
a fi xed 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 V
used. There is an equivalent 50k resistor from PWM pin
to ground internally.
PIN FUNCTIONS
6
IN
REF
T
: Switching Frequency Adjustment Pin. Set switching
: Input Supply Pin. Must be locally bypassed.
: Reference Output Pin. This pin can supply up to
T
resistor should be chosen to pro-
REF
pin or SHDN pin if not
CTRL: LED Current Adjustment Pin. Sets voltage across
sense resistor between ISP and ISN. Connect directly to
V
between GND and 1V to modulate LED current. Tie the CTRL
pin to the V
V
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 amplifi er.
ISP: Current Sense (+) Pin. The noninverting input to the
current sense amplifi er. Also serves as positive rail for
TG pin driver.
TG: Top Gate Driver Output. An inverted PWM sig-
nal drives series PMOS device between V
(V
Leave TG unconnected if not used.
Ground: Exposed Pad. Solder paddle directly to ground
plane.
REF
C
ISP
: g
for full-scale threshold of 100mV, or use signal values
m
– 7V). An internal 7V clamp protects the PMOS gate.
Error Amplifi er Output Pin. Stabilize the loop with
REF
pin if not used.
ISP
and
3517f