LT3593ES6#PBF Linear Technology, LT3593ES6#PBF Datasheet - Page 7

• Manufacturer Part Number: LT3593ES6#PBF
• Manufacturer: Linear Technology

Specifications of LT3593ES6#PBF

• Operating Supply Voltage (typ): 3.3/5V
• Number Of Segments: 10
• Operating Temperature (min): -40C
• Operating Temperature (max): 85C
• Operating Temperature Classification: Industrial
• Package Type: TSOT-23
• Pin Count: 6
• Mounting: Surface Mount
• Operating Supply Voltage (min): 2.7V
• Operating Supply Voltage (max): 5.5V
• Lead Free Status / Rohs Status: Compliant

OPERATION
The LT3593 uses a constant frequency, current mode
control boost scheme to provide excellent line and load
regulation. Operation can be best understood by referring
to the Block Diagram in Figure 1.
Output Disconnect
An internal switch connects between the CAP pin and the
LED pin. The top of the LED string is connected to the
LED pin. The string can be terminated to ground or to
V
in shutdown, the switch is off; allowing no current to run
through the LEDs.
Current Programming
The LED current can be set to 32 different values
(625μA – 20mA) by strobing the CTRL pin. A 5-bit
counter is decremented by 1 on a CTRL pin rising edge,
reducing the programmed current by 625μA each time.
IN
if a low number of LEDs are driven. When the part is
CURRENT
CTRL
LED
CTRL
CTRL
CTRL
CTRL
128μs
20mA
Figure 3. Current Programming and Shutdown Timing
20mA
Figure 2. Current Programming
The desired current can be calculated by:
where N is the number of rising edges. When the desired
current setting is reached, the CTRL pin must stay high.
128μs after the last rising edge on the CTRL pin, the
regulator will enable the output and start to regulate the
LED current to the programmed value. Figure 2 shows
an example of how the part can be programmed.
If a different current is desired, the CTRL pin can be strobed
again. The fi rst falling edge will reset the internal register
to the 20mA setting. While the new current is being pro-
grammed, the device will continue to regulate the previously
programmed value until the CTRL pin has remained high
for at least 128μs, at which time the regulated current will
slew to the newly programmed value. Figure 3 shows how
to program a new LED current level.
If the CTRL pin is held low for longer than 128μs, the part
will go into the shutdown mode.
I
LED
128μs
= 20mA – (N – 1) • 625μA
17.5mA
17.5mA
3593 F02
FULL CURRENT
20mA
17.5mA
15mA
12.5mA
128μs
SHDN
3593 F03
LT3593
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3593f