lt3593 Linear Technology Corporation, lt3593 Datasheet - Page 6

• Manufacturer Part Number: lt3593
• Description: 1mhz White Led Driver With Output Disconnect And One Pin Current Programming
• Manufacturer: Linear Technology Corporation

PIN FUNCTIONS
LT3593
V
passed with a 1μF X5R or X7R type ceramic capacitor.
GND (Pin 2/Pin 2): Ground Pin. Connect directly to local
ground plane.
SW (Pin 6/Pin 4): Switch Pin. Connect inductor between
this pin and the V
to minimize EMI.
CAP (Pin 5/Pin 5): Output Pin. Connect to output capaci-
tor. Minimize trace between this pin and output capacitor
to reduce EMI.
CTRL (Pin 3/Pin 1): Current Control and Shutdown Pin.
This pin is used to program the LED output current. This
pin is strobed up to 32 times to decrement the internal
5-bit DACs from full-scale to 1LSB. The counter will stop
at 1LSB if the strobing continues beyond 32 counts.
BLOCK DIAGRAM
6
IN
(Pin 1/Pin 3): Input Supply Pin. Must be locally by-
PIN NUMBERS REFER TO DFN PACKAGE. REFER TO PIN CONFIGURATION FOR TSOT PIN NUMBERS
IN
SHDN
pin. Minimize inductance at this pin
1.24V
V
(DFN/TSOT)
REF
1
V
IN
OSCILLATOR
GENERATOR
RAMP
+
–
–
+
A2
Figure 1. Block Diagram
R
C
C
COMP
PWM
C
R
S
The pin must be held high after the fi nal desired positive
strobe edge. The data is transferred after a 128μs (typ)
delay. The part can be reprogrammed to a different value
after it has been enabled, however the current will change
to the new value after 128μs. If CTRL is held low for longer
than 128μs (typ), the part will go into shutdown.
LED (Pin 4/Pin 6): LED Pin. An internal switch connects
this pin to CAP . The top of the LED string is connected
to this pin. When the part is in shutdown, the LED pin is
switched off from CAP so no current runs through the
LEDs. The switch is also used to sense the LED current
when the part is on.
Exposed Pad (Pin 7/NA): Ground. The Exposed Pad must
be soldered to the PCB.
Q
A1
+
–
DRIVER
A3
7
+
–
6
2
Q1
SW
GND
R
LINEAR DAC
OVERVOLTAGE
COUNTER
PROTECTION
M2
5-BIT
5-BIT
3
CTRL
SHDN
SHDN
CAP
LED
M1
3593 F01
5
4
3593f