CAT3616 Datasheet, PDF (11/14 Pages) Catalyst Semiconductor – 6-Channel Charge Pump LED Driver with EZDimTM

CAT3616
LED Current Setting
The LED current is controlled by toggling the input
signals ENM and ENS. ENM controls the four LED
channels MAIN1 to MAIN4. ENS controls the two LED
lines SUB1 and SUB2. ENM and ENS work the same way.
The chip must first be enabled by setting the enable input EN
high. On the first ENM or ENS transition from high to low,
the LED current in the associated LEDs is set to the full scale
31 mA. On each consecutive falling edge of ENM or ENS,
the LED current is decreased by 1 mA. On the 32^nd pulse, the
LED channel is turned off and the current drops to 0 mA.
One additional ENM or ENS pulse resets the full current to
31 mA, as shown on Figure 2.
Consecutive pulses should be separated by 300 ns or
more. Pulsing frequencies from 5 kHz up to 1 MHz are
supported during dimming operations. When the EN is held
low for 1.5 ms or more, the CAT3616 enters the shutdown
mode and draws “zero” current. When the enable EN input
is low, toggling ENM or ENS has no effect.
Unused LED channels can be disabled independently by
connecting the corresponding main or sub LED pin to
VOUT.
Protection Mode
If an LED becomes open−circuit, the output voltage
VOUT is internally limited to about 5.5 V. This is to prevent
the output pin from exceeding its absolute maximum rating.
The driver enters a thermal shutdown mode as soon as the
die temperature exceeds about +165°C. When the device
temperature drops down by about 20°C, the device resumes
normal operation.
External Components
The driver requires a total of four external 1 mF ceramic
capacitors: two for decoupling input and output, and two for
the charge pump. Both capacitor types X5R and X7R are
recommended for the LED driver application. In the 1.5x
charge pump mode, the input current ripple is kept very low
by design, and an input bypass capacitor of 1 mF is sufficient.
In 1x mode, the device operating in linear mode does not
introduce switching noise back onto the supply.
Recommended Layout
In 1.5x charge pump mode, the driver switches internally
at a high frequency of 1 MHz. It is recommended to
minimize trace length to all four capacitors. A ground plane
should cover the area under the driver IC as well as the
bypass capacitors. Short connection to ground on capacitors
Cin and Cout can be implemented with the use of multiple
via. A copper area matching the TDFN exposed pad (GND)
must be connected to the ground plane underneath. The use
of multiple via improves the package heat dissipation.
http://onsemi.com
11