LTC3219 Datasheet, PDF (10/20 Pages) Linear Technology – 250mA Universal Nine Channel LED Driver

LTC3219
OPERATION
To use the ENU pin, the I²C port must first be configured
to select the desired LED outputs. When ENU is high, the
selected displays will be enabled as per the REG10 and
REG11 settings. When ENU is Low the selected displays
will be off. If no other displays are programmed to be
enabled, the chip will be in shutdown.
Gradation can also be pre-programmed for control by
the ENU pin. The registers are written as required per
the gradation description and the UP bit is ignored. The
registers are programmed when ENU is low. When ENU is
set high, the part will become enabled and the selected LED
outputs will ramp up. When ENU is set low the selected
LED outputs will ramp low to zero current and then the
part will shut down. The charge pump must not be in a
forced mode if shutdown is required.
If the ENU pin is not used, it is connected to ground. If
ENU is used and other ULED outputs are active then ENU
will reset the charge pump mode to 1x on the falling edge.
Please refer to Application Note 111 for detailed informa-
tion and examples on programming ENU control.
Shutdown Current
Shutdown occurs when all the current source data bits have
been written to zero, DV_CC is set below the undervoltage
lockout voltage or when ENU switches low (all other outputs
disabled). The charge pump must also be in auto mode.
Although the LTC3219 is designed to have very low shut-
down current, it will draw about 3.2μA from V_BAT when
in shutdown. Internal logic ensures that the LTC3219 is
in shutdown when DV_CC is low. Note, however that all of
the logic signals that are referenced to DV_CC (SCL, SDA,
ENU) will need to be at DV_CC or below (i.e., ground) to
avoid violation of the absolute maximum specifications
on these pins.
EMI Reduction
The flying capacitor pins C1M, C1P, C2M and C2P have
controlled slew rates to reduce conducted and radiated
noise.
Serial Port
The microcontroller compatible I²C serial port provides all
of the command and control inputs for the LTC3219. Data
on the SDA input is loaded on the rising edge of SCL. D7
is loaded first and D0 last. There are 12 data registers, one
address register and one sub-address register. Once all
address bits have been clocked into the address register
acknowledge occurs. The sub-address register is then
written followed by writing the data register. Each data
register has a sub-address. After the data register has been
written a load pulse is created after the stop bit. The load
pulse transfers all of the data held in the data registers
to the DAC registers. The stop bit can be delayed until
all of the data master registers have been written. At this
point the LED current will be changed to the new settings.
The serial port uses static logic registers so there is no
minimum speed at which it can be operated.
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