ADP8860 Analog Devices, ADP8860 Datasheet - Page 21

• Manufacturer Part Number: ADP8860
• Description: Charge Pump, 7-Channel Smart LED Driver with I2C Interface
• Manufacturer: Analog Devices

Specifications of ADP8860

• Vin Range: 2.4V to 5.5V
• Vout (v): 4.3 to 5.5
• Synchronous: No
• Package: 20-Lead WLCSP
• Led Configuration: Parallel
• Topology: Capacitive
• I2c Support: Yes
• Max Iout (ma): 60mA
• Brightness Control: I2C
• Peak Efficiency (%): 89%
• Switching Frequency: 1MHz

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, it 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 ADP8860 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 start-up and restart attempts (fault recovery). SCP
sensing reenables 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
large, the device inadvertently enters short-circuit protection.
OVERVOLTAGE PROTECTION
Overvoltage protection (OVP) is implemented on the output.
There are two types of overvoltage events: normal (no fault) and
abnormal (from a fault or sudden load change).
Normal Overvoltage
In a normal (no fault) overvoltage, the output voltage approaches
V
caused by a fault or load change, but it is simply a consequence
of the input voltage times the gain reaching the same level as the
clamped output voltage (V
MAX
OUT(REG)
CURRENT
SCx
SCx_EN
SET BY USER
FADE-IN
(4.9 V typical) during normal operation. This is not
Figure 41. Independent Sink Blink Mode with Fading
IN
ON TIME
within the 4 ms (typical) time. If C
FADE-OUT FADE-IN
IN
. Note that this SCP sensing is disabled
OUT(REG)
TIME
OFF
). To prevent this type of over-
ON TIME
FADE-OUT
OUT
TIME
OUT
OFF
) should be
is too
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voltage, the ADP8860 detects when the output voltage rises to
V
reduce the voltage that is delivered. This effectively regulates
V
system can have on regulating V
operation and it is not intended to protect against faults or sudden
load changes. When the output voltage is regulated to V
no interrupt is set and the operation is transparent to the LEDs
and the overall application.
Abnormal Overvoltage
Because of the open-loop behavior of the charge pump as well
as how the gain transitions are computed, a sudden load change
or fault can abnormally force V
abnormal overvoltage situation. If the event happens slowly
enough, the system first tries to regulate the output to 4.9 V as
in a normal overvoltage scenario. However, if this is not
sufficient, or if the event happens too quickly, then the
ADP8860 enters overvoltage protection (OVP) mode when
V
mode, only the charge pump is disabled to prevent V
rising too high. The current sources and all other device
functionality remain intact. When the output voltage falls by
about 500 mV (to 5.3 V typical), the charge pump resumes
operation. If the fault or load step recurs, the process may
repeat. An interrupt flag is set at each OVP instance.
THERMAL SHUTDOWN/OVERTEMPERATURE
PROTECTION
If the die temperature of the ADP8860 rises above a safe limit
(150°C typical), the controllers enter thermal shutdown (TSD)
protection mode. In this mode, most of the internal functions
shut down, the part enters standby, and the TSD_INT interrupt
is set. When the die temperature decreases below ~130°C, the
part can be restarted. To restart the part, simply remove it from
standby. No interrupt is generated when the die temperature
falls below 130°C. However, if the software clears the pending
TSD_INT interrupt and the temperature remains above 130°C,
another interrupt is generated.
The complete state machine for these faults (SCP, OVP, and
TSD) is shown in Figure 42.
OUT(REG)
OUT
OUT
to V
exceeds the OVP threshold (typically 5.8 V). In the OVP
. It then increases the effective R
OUT(REG)
; however, there is a limit to the effect that this
OUT
OUT
. It is designed only for normal
beyond 6 V. This causes an
OUT
of the gain stage to
ADP8860
OUT
OUT(REG)
from