ADP1196(Rev0) Просмотр технического описания (PDF) - Analog Devices
Номер в каталоге
Компоненты Описание
производитель
ADP1196 Datasheet PDF : 12 Pages
| |||
Data Sheet
TIMING
Turn-on delay is defined as the interval between the time that
VVB_EN exceeds the rising threshold voltage and when VOUT rises
to ~10% of its final value. The ADP1196 includes circuitry that has
a typical 2 ms turn-on delay and a controlled rise time to limit
the VIN inrush current. As shown in Figure 25 and Figure 26,
the turn-on delay is nearly independent of the input voltage.
T
2
ENABLE
1
INPUT CURRENT
VOUT
3
CH1 20mAΩ BW
CH3 500mV BW
CH2 1V BW
M1ms
T 10.6%
A CH2 1.18V
Figure 25. Typical Turn-On Time and Inrush Current,
VIN = 1.8 V, COUT = 47 μF, 330 Ω Load
T
2
ENABLE
1
INPUT CURRENT
VOUT
3
CH1 20mAΩ BW
CH3 2V BW
CH2 1V BW
M1ms
T 10.6%
A CH2 1.18V
Figure 26. Typical Turn-On Time and Inrush Current,
VIN = 5 V, COUT = 47 μF, 330 Ω Load
The rise time is defined as the time it takes the output voltage
(VOUT) to rise from 10% to 90% of its final value. The output
voltage rise time 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 (CLOAD) and R is the RDSON||RLOAD)
can become a factor in the rise time of the output voltage. Because
RDSON is much smaller than RLOAD, an adequate approximation
for RC is RDSON × CLOAD. An input or load capacitor is not required
for the ADP1196, although capacitors can be used to suppress
noise on the board.
ADP1196
The turn-off time is defined as the time it takes for the output
voltage to fall from 90% to 10% of VOUT. It is also dependent on
the RC time constant of the output capacitance and load resistance.
Figure 27 shows the typical turn-off times with VIN = 1.8 V, VIN =
3.3 V, and VIN = 5.0 V, COUT = 47 μF, and RLOAD = 330 Ω.
6.0
VVB_EN
VIN = 5.0V
5.0
VIN = 3.3V
VIN = 1.8V
4.0
3.0
2.0
1.0
0
0 0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.08 0.09 0.10
TIME (SEC)
Figure 27. Typical Turn-Off Time, VIN = 1.8 , VIN = 3.3 V, and VIN = 5.0 V,
COUT = 47 μF, RLOAD = 330 Ω
CURRENT-LIMIT AND THERMAL OVERLOAD
PROTECTION
The ADP1196 is protected against damage due to excessive power
dissipation by current and thermal overload protection circuits.
The ADP1196 is designed to limit current when the output load
reaches 4 A. When the output load exceeds 4 A, the output voltage
is reduced to maintain a constant current limit.
Thermal overload protection is included, which limits the junction
temperature to a maximum of 125°C (typical). Under extreme
conditions (that is, high ambient temperature and/or high power
dissipation), when the junction temperature starts to rise above
125°C, the output is turned off, reducing the output current to
zero. When the junction temperature falls below 110°C, the
output is turned on again, and output current is restored to its
operating value.
Consider the case where a hard short from VOUT to GND occurs.
At first, the ADP1196 limits current, so that only 4 A conducts into
the short. If the self-heating of the junction is great enough to
cause its temperature to rise above 125°C, thermal shutdown is
activated, turning off the output and reducing the output current to
zero. As the junction temperature cools and falls below 110°C, the
output turns on and conducts 4 A into the short, again causing the
junction temperature to rise above 125°C. This thermal oscillation
between 110°C and 125°C causes a current oscillation between 4 A
and 0 mA that continues as long as the short remains at the output.
Current and thermal limit protections are intended to protect
the device against accidental overload conditions. For reliable
operation, device power dissipation must be externally limited
so that junction temperature does not exceed 125°C.
Rev. 0 | Page 11 of 12
Share Link: 