ADP8861 Analog Devices, ADP8861 Datasheet - Page 16

• Manufacturer Part Number: ADP8861
• Description: Charge Pump, 7-Channel Smart LED Driver with I2C Interface
• Manufacturer: Analog Devices

Specifications of ADP8861

• Vin Range: 2.5 to 5.5V
• Vout (v): 4.3 to 5.5
• Synchronous: No
• Package: 20-Lead LFCSP,20-Lead WLCSP
• Led Configuration: Parallel
• Topology: Capacitive
• I2c Support: Yes
• Max Iout (ma): 60mA
• Brightness Control: PWM
• Peak Efficiency (%): 89%
• Switching Frequency: 1.32MHz
• Over Volt Protection (v): 5.8V

ADP8861
The dim timer and off timer can be used together for sequential
maximum-to-dim-to-off functionality. With both the dim and
off timers programmed, and BL_EN asserted, the backlight turns
on to its maximum setting, and when the dim timer expires, the
backlight changes to its dim setting. When the off timer expires,
the backlight turns off.
FADE OVERRIDE
A fade override feature (FOVR in Register CFGR (0x04)) enables
the host to override the preprogrammed fade in or fade out set-
tings. If FOVR is set and the backlight is enabled in the middle
of a fade out process, the backlight instantly (within approximately
100 ms) returns to its prefade brightness level. Alternatively, if
the backlight is fading in, reasserting BL_EN overrides the pro-
grammed fade in time, and the backlight instantly goes to its final
fade value. This is useful for situations where a key is pressed
during a fade sequence. However, if FOVR is cleared and the
backlight is enabled in the middle of a fade process, the back-
light gradually brightens from where it was interrupted (it does
not go down to 0 and then comes back on).
BACKLIGHT
MAX
BACKLIGHT
MAX
DIM
CURRENT
CURRENT
BL_EN = 1
SET BY USER
SET BY INTERNAL STATE MACHINE
OVERRIDDEN
Figure 36. Fade Override Function (FOVR Is High)
(REASSERTED)
Figure 35. Dim and Off Timers Used Together
BL_EN = 1
FADE-IN
BL_EN = 1
DIM TIMER
RUNNING
DIM_EN = 1
BL_EN = 0 BL_EN = 1 BL_EN = 0
OFF TIMER
RUNNING
OVERRIDDEN
FADE-OUT
BL_EN = 0
Rev. A | Page 16 of 40
INDEPENDENT SINK CONTROL
Each of the seven LEDs can be configured (in Register 0x05) to
operate as either part of the backlight or to operate as an indepen-
dent sink current (ISC). Each ISC can be enabled independently
and has its own current level. All ISCs share the same fade in
rates, fade out rates, and fade law.
The ISCs have additional timers to facilitate blinking functions.
A shared on timer (SCON) used in conjunction with the off
timers of each ISC (SC1_OFF, SC2_OFF, SC3_OFF, and SC4_OFF
in Register 0x12, and SC5_OFF, SC6_OFF, and SC7_OFF in
Register 0x11) allows the LED current sinks to be configured in
various blinking modes. The on timer can be set to one of four
different settings: 0.2 sec, 0.6 sec, 0.8 sec, or 1.2 sec. The off
timers have four different settings: disabled, 0.6 sec, 1.2 sec, and
1.8 sec. Blink mode is activated by setting the off timers to any
setting other than disabled.
Program all fade, on, and off timers before enabling any of the
LED current sinks. If ISCx is on during a blink cycle and
SCx_EN is cleared, the LED turns off (or fades to off if fade out
is enabled). If ISCx is off during a blink cycle and SCx_EN is
cleared, it stays off.
SHORT-CIRCUIT PROTECTION MODE
The ADP8861 can protect against short circuits on the output
(VOUT). Short-circuit protection (SCP) is activated at the point
when VOUT < 55% of V
during both startup and restart attempts (fault recovery). SCP
sensing is reenabled 4 ms (typical) after activation. During a
short-circuit fault, the device enters a low current consumption
state and an interrupt flag is set. The device can be restarted at
any time after receiving a short-circuit fault by simply rewriting
nSTBY = 1. It then repeats another complete soft start sequence.
Note that the value of the output capacitance (C
small enough to allow VOUT to reach approximately 55% (typical)
of V
device inadvertently enters short-circuit protection.
MAX
ISCx
IN
ISCx_EN
within the 4 ms (typical) time. If C
SET BY USER
FADE-IN
Figure 37. Independent Sink Blink Mode with Fading
ON TIME
FADE-OUT FADE-IN
IN
. Note that SCP sensing is disabled
TIME
OFF
ON TIME
OUT
FADE-OUT
is too large, the
OUT
TIME
OFF
) should be