LTC3210EPD-1-TRPBF datasheet(9/16 Pages) LINER

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LTC3210-1

32101fc

Power Management

The LTC3210-1 uses a switched capacitor charge pump

to boost CPO to as much as 2 times the input voltage up

to 5.1V. The part starts up in 1x mode. In this mode, VBAT

is connected directly to CPO. This mode provides maxi-

mum efﬁciency and minimum noise. The LTC3210-1 will

remain in 1x mode until an LED current source drops out.

Dropout occurs when a current source voltage becomes

too low for the programmed current to be supplied. When

dropout is detected, the LTC3210-1 will switch into 1.5x

mode. The CPO voltage will then start to increase and will

attempt to reach 1.5x VBAT up to 4.6V. Any subsequent

dropout will cause the part to enter the 2x mode. The CPO

voltage will attempt to reach 2x VBAT up to 5.1V. The part

will be reset to 1x mode whenever the part is shut down

or when ENC goes low.

A two phase nonoverlapping clock activates the charge

pump switches. In the 2x mode the ﬂying capacitors are

charged on alternate clock phases from VBAT to minimize

input current ripple and CPO voltage ripple. In 1.5x mode the

ﬂying capacitors are charged in series during the ﬁrst clock

phase and stacked in parallel on VBAT during the second

phase. This sequence of charging and discharging the ﬂying

capacitors continues at a constant frequency of 800kHz.

LED Current Control

The MLED currents are delivered by the four program-

mable current sources. 64 linear current settings (0mA

to 20mA, RM = 30.1k) are available by strobing the ENM

pin. Each positive strobe edge decrements a 6-bit down

counter which controls a 6-bit linear DAC. When the

Figure 1. Current Programming Timing Diagram

desired current is achieved ENM is stopped high. The

output current then changes to the programmed value

after 150μs (typ). The counter will stop when the LSB

is reached. The output current is set to 0 when ENM is

toggled low after the output has been enabled. If strobing

is started within 150μs (typ), after ENM has been set low,

the counter will continue to count down. After 150μs (typ)

the counter is reset.

The CLED current is delivered by a programmable current

source. Eight linear current settings (0mA to 380mA, RC

= 24.3k) are available by strobing the ENC pin. Each posi-

tive strobe edge decrements a 3-bit down counter which

controls a 3-bit linear DAC. When the desired current is

reached, ENC is stopped high. The output current then

changes to the programmed value after 150μs (typ). The

counter will stop when the LSB is reached. The output

current is set to 0 when ENC is toggled low after the output

has been enabled. If strobing is started within 150μs (typ)

after ENC has been set low, the counter will continue to

count down. After 150μs (typ) the counter is reset.

The full-scale output current is calculated as follows:

MLED full-scale output current

(1.215V/(RM + 500)) • 535

CLED full-scale output current

(1.215V/(RC + 500)) • 7700

When both ENM and ENC are held low for more than

150μs (typ) the part will go into shutdown. See Figure 1

for timing information.

ENC resets the mode to 1x on a falling edge.

tPW ≥ 200ns

ENM = ENC = LOW

SHUTDOWN

tEN 150μs (TYP)

tSD 150μs (TYP)

PROGRAMMED

CURRENT

ENM

OR ENC

LED

CURRENT

32101 F01

OPERATION

LTC3210EPD-1-TRPBF Datasheet(PDF) 9 Page - Linear Technology

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