ADP1290
Data Sheet
APPLICATIONS INFORMATION
CAPACITOR SELECTION
ENABLE FEATURE
The ADP1290 uses the EN pin to enable and disable the VOUT
pin under normal operating conditions. As shown in Figure 22,
when a rising voltage (VEN) on the EN pin crosses the active
Output Capacitor
The ADP1290 is designed for operation with small, space-
saving ceramic capacitors but functions with most commonly
used capacitors when the effective series resistance (ESR) value
is carefully considered. The ESR of the output capacitor affects
the response to load transients. A typical 1 µF capacitor with an
ESR of 0.1 Ω or less is recommended for good transient response.
Using a larger value of output capacitance improves the transient
response to large changes in load current.
threshold, the VOUT pin turns on. When a falling voltage (VEN
)
on the EN pin crosses the inactive threshold, the VOUT pin
turns off.
6
5
4
Input Bypass Capacitor
Connecting at least 1 µF of capacitance from VIN to GND reduces
the circuit sensitivity to the PCB layout, especially when high
source impedance or long input traces are encountered. When
an output capacitance of greater than 1 µF is required, increase
the input capacitor to match it.
V
V
AT 2.3V
AT 5.0V
OUT
3
2
1
0
OUT
V
FALLING
EN
V
RISING
EN
GROUND CURRENT
The major source for ground current in the ADP1290 is the
internal charge pump for the FET drive circuitry. Figure 21
shows the typical ground current when VEN = VIN and varies
from 2.3 V to 13.2 V.
0.50 0.55 0.60 0.65 0.70 0.75 0.80 0.85 0.90 0.95 1.00
ENABLE VOLTAGE (V)
Figure 22. Typical EN Operation
As shown in Figure 22, the EN pin has hysteresis built into it.
The hysteresis prevents on/off oscillations that can occur due to
noise on the EN pin as it passes through the threshold points.
25
20
15
The EN pin rising and falling thresholds derive from the VIN
voltage; therefore, these thresholds vary with the changing input
voltage. Figure 23 shows the typical EN rising and falling
thresholds when the input voltage varies from 2.3 V to 13.2 V.
0.9
I
I
I
I
I
= 50mA
LOAD
LOAD
LOAD
LOAD
LOAD
10
5
= 100mA
= 200mA
= 500mA
= 1000mA
= 2000mA
0.8
0.7
0.6
I
LOAD
0
2
4
6
8
10
12
14
EN RISE
EN FALL
0.5
INPUT VOLTAGE (V)
0.4
0.3
0.2
0.1
0
Figure 21. Ground Current vs. Input Voltage (VIN), Different Load Currents (ILOAD
)
2
4
6
8
10
12
14
V
(V)
IN
Figure 23. Typical EN Thresholds (Rising and Falling) vs. Input Voltage (VIN
)
Rev. 0 | Page 10 of 12