Data Sheet ADP1290
TIMING
Turn on delay is defined as the interval between the time that
V
EN
exceeds the rising threshold voltage and when V
OUT
rises to
~10% of its final value. The ADP1290 includes circuitry that has
a typical 250 μs turn on delay and a controlled rise time to limit
the V
IN
inrush current. As shown in Figure 24 and Figure 25,
the turn on delay is nearly independent of the input voltage.
12529-024
CH1 2.00V
B
W
CH3 100mAΩ
B
W
CH2 2.00V
B
W
M400µs A CH4 1.04V
T
10.40%
2
1
3
EN
INPUT CURRENT
OUTPUT
Figure 24. Typical Turn On Time and Inrush Current, V
IN
= 2.5 V,
C
OUT
= 10 μF, R
LOAD
= 100 Ω
12529-025
CH1 2.00V
B
W
CH3 200mAΩ
B
W
CH2 5.00V
B
W
M400µs A CH4 1.04V
T 10.40%
2
1
3
EN
INPUT CURRENT
OUTPUT
Figure 25. Typical Turn On Time and Inrush Current, V
IN
= 6.5 V,
C
OUT
= 10 μF, R
LOAD
= 100 Ω
The rise time is defined as the time it takes the output voltage
to rise from 10% to 90% of V
OUT
reaching its final value. The turn
on delay is dependent on the rise time of the internal charge pump.
For very large values of output capacitance, the RC time constant
(where C is the load capacitance, C
LOAD
, and R is the RDS
ON
||R
LOAD
)
can become a factor in the rise time of the output voltage. Because
RDS
ON
is much smaller than R
LOAD
, an adequate approximation for
RC is RDS
ON
× C
LOAD
. An input or load capacitor is not required for
the ADP1290; however, capacitors can suppress noise on the board.
The turn off time is defined as the time it takes for the output
voltage to fall from 90% to 10% of V
OUT
reaching its final value. The
turn off time is also dependent on the RC time constant of the
output capacitance (C
LOAD
) and load resistance (R
LOAD
).
Figure 26 and Figure 27 show the typical turn off times with
V
IN
= 6.5 V, C
OUT
= 10 μF and 100 μF, and R
LOAD
= 100 Ω.
12529-026
CH1 2.00V
B
W
CH2 2.00V
B
W
M400µs
A CH4 1.04V
T 10.40%
2
1
EN
OUTPUT
Figure 26. Typical Turn Off Time, C
OUT
= 10 μF, R
LOAD
= 100 Ω
12529-027
CH1 1.00V
B
W
CH2 2.00V
B
W
M400µs A CH4 1.08V
T 10.40%
2
1
EN
OUTPUT
Figure 27. Typical Turn Off Time, C
OUT
= 100 μF, R
LOAD
= 100 Ω
CURRENT AND THERMAL OVERLOAD
PRECAUTIONS
The ADP1290 is not protected against damage due to excessive
power dissipation and does not have thermal overload protection
circuits. To prevent permanent damage, never allow current
through the ADP1290 to exceed its rated value for more than a
few milliseconds. Permanent damage can also occur if the
output is shorted to ground
THERMAL CONSIDERATIONS
To guarantee reliable operation, the junction temperature of the
ADP1290 must not exceed 105°C. To ensure that the junction
temperature stays below this maximum value, the user must be
aware of the parameters that contribute to junction temperature
changes. These parameters include ambient temperature, power
dissipation in the power device, and thermal resistances between
the junction and ambient air (θ
JA
). The θ
JA
number is dependent
on the package assembly and the amount of copper used to solder
the package pins to the PCB.
Rev. 0 | Page 11 of 12
