ADP8866 Analog Devices, ADP8866 Datasheet - Page 13

• Manufacturer Part Number: ADP8866
• Description: Charge Pump Driven 9-Channel LED Driver with Automated LED Lighting Effects
• Manufacturer: Analog Devices

Specifications of ADP8866

• Vin Range: 2.5 to 5.5V
• Vout (v): 4.3 to 5.5
• Synchronous: No
• Package: 20-Lead LFCSP
• Led Configuration: Parallel
• Topology: Capacitive
• I2c Support: Yes
• Max Iout (ma): 25mA
• Brightness Control: I2C
• Peak Efficiency (%): 92%
• Switching Frequency: 1MHz

Note that the gain selection criteria applies only to active
current sources. If a current source has been deactivated
through an I
an application), the voltages on the deactivated current sources
are ignored.
Soft Start Feature
At startup (either from UVLO activation or fault/standby
recovery), the output is first charged by I
until it reaches about 92% of V
the inrush current that is otherwise present when the output
capacitance is initially charged to V
reached, the controller enters 1× mode. If the output voltage is
not sufficient, the automatic gain selection determines the
optimal point as defined in the Automatic Gain Selection section.
OPERATING MODES
There are four different operating modes: active, standby,
shutdown, and reset.
Active Mode
In active mode, all circuits are powered up and in a fully
operational state. This mode is entered when nSTBY (in
Register MDCR) is set to 1.
Standby Mode
Standby mode disables all circuitry except for the I
Current consumption is reduced to less than 1 μA. This mode is
entered when nSTBY is set to 0 or when the nRST pin is held
nSTBY
nRST
V
OUT
V
IN
2
C command (that is, only five LEDs are used for
SHUTDOWN
V
IN
V
IN
IN
~100µs DELAY BETWEEN POWER UP AND
WHEN I
. This soft start feature reduces
CROSSES ~2.0V AND TRIGGERS POWER ON RESET
BIT nSTBY IN REGISTER
MDCR GOES HIGH
IN
~7.0mA CHARGES
V
. When this point is
OUT
2
C COMMANDS CAN BE RECEIVED
SOFT START
SS
TO V
(7.0 mA typical)
IN
25µs TO 100µs NOISE FILTER
LEVEL
2
C receivers.
Figure 29. Typical Timing Diagram
10µs 100µs
Rev. 0 | Page 13 of 52
1×
1.5×
low for more than 100 μs (maximum). When standby is exited,
a soft start sequence is performed.
Shutdown Mode
Shutdown mode disables all circuitry, including the I
Shutdown occurs when V
When V
reset and the part is placed into standby mode.
Reset Mode
In reset mode, all registers are set to their default values and the
part is placed into standby. There are two ways to reset the part:
power on reset (POR) and the nRST pin. POR is activated any-
time that the part exits shutdown mode. After a POR sequence
is complete, the part automatically enters standby mode.
After startup, the part can be reset by pulling the nRST pin low.
As long as the nRST pin is low, the part is held in a standby state
but no I
at their default values). After releasing the nRST pin, all registers
remain at their default values, and the part remains in standby;
however, the part does accept I
The nRST pin has a 50 μs (typical) noise filter to prevent inad-
vertent activation of the reset function. The nRST pin must be
held low for this entire time to activate reset.
The operating modes function according to the timing diagram
in Figure 29.
2×
GAIN CHANGES ONLY OCCUR WHEN NECESSARY
BUT HAVE A MINIMUM TIME BEFORE
CHANGING
2
IN
C commands are acknowledged (all registers are kept
rises above V
nRST IS LOW, WHICH FORCES nSTBY LOW
AND RESETS ALL I
nRST MUST BE HIGH FOR 20µs (MAX)
BEFORE SENDING I
IN(START)
IN
is below the undervoltage thresholds.
2
C REGISTERS
2
(2.0 V typical), all registers are
SOFT START
C commands.
2
C COMMANDS
ADP8866
2
C receivers.