Datasheet

LT3593
6
3593f
PIN FUNCTIONS
(DFN/TSOT)
BLOCK DIAGRAM
V
IN
(Pin 1/Pin 3): Input Supply Pin. Must be locally by-
passed with a 1F 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
IN
pin. Minimize inductance at this pin
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.
The pin must be held high after the fi nal desired positive
strobe edge. The data is transferred after a 128s (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 128s (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.
61
–
+
–
+
R
SWV
IN
CAP
Q
S
DRIVER
OVERVOLTAGE
PROTECTION
RAMP
GENERATOR
OSCILLATOR
V
REF
1.24V
SHDN
Q1
R
–
+
LED
3593 F01
GND
PIN NUMBERS REFER TO DFN PACKAGE. REFER TO PIN CONFIGURATION FOR TSOT PIN NUMBERS
CTRL
SHDN
A1
R
C
C
C
A2
A3
SHDN
M2 M1
PWM
COMP
5-BIT
LINEAR DAC
5-BIT
COUNTER
+
–
27 3
4
5
Figure 1. Block Diagram