Datasheet

ADP199 Data Sheet
Rev. A | Page 12 of 16
APPLICATIONS INFORMATION
GROUND CURRENT
The major source for ground current in the ADP199 is the internal
charge pump for the FET drive circuitry. Figure 30 shows the
typical ground current when V
EN
= V
IN
, and varies from 1.1 V
to 3.6 V.
0
5
10
15
20
25
30
35
40
45
50
0.8 1.2 1.6 2.0 2.4 2.8 3.2 3.6
GROUND CURRENT (µA)
V
IN
(V)
5mA
10mA
50mA
100mA
200mA
500mA
09672-030
Figure 30. Ground Current vs. Input Voltage, Different Load Current
ENABLE FEATURE
The ADP199 uses the EN input to enable and disable the V
OUT
output. As shown in Figure 31, when a rising voltage (V
EN
) on
the EN pin crosses the active threshold, V
OUT
turns on. When
a falling voltage (V
EN
) on the EN pin crosses the inactive
threshold, V
OUT
turns off.
09672-031
0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
1.2 1.3 1.4 1.5 1.6 1.7 1.8 1.9 2.0 2.1
ENABLE VOLTAGE (V)
OUTPUT VOLTAGE (V)
V
OUT
AT 3.3V
Figure 31. Typical EN Operation, V
IN
= 3.3 V
ENABLE VOLTAGE (V)
0
0.2
0.4
0.6
0.8
1.0
1.2
1.4
0.30 0.35 0.40 0.45 0.50 0.55 0.60 0.65 0.70
OUTPUT VOLTAGE (V)
V
OUT
AT 1.2V
09672-032
Figure 32. Typical EN Operation, V
IN
= 1.2 V
As shown in Figure 31, the EN pin has hysteresis built into it.
This prevents on/off oscillations that can occur due to noise on
the EN pin as it passes through the threshold points.
The EN pin active/inactive thresholds derive from the V
IN
voltage;
therefore, these thresholds vary with the changing input voltage.
Figure 33 shows the typical EN active/inactive thresholds when
the input voltage varies from 1.1 V to 3.6 V.
0
0.5
1.0
1.5
2.0
2.5
1.0 1.5 2.0 2.5
3.0 3.5
THRESHOLDS
INPUT VOLTAGE (V)
EN RISE
EN FALL
09672-033
Figure 33. Typical EN Thresholds vs. Input Voltage (V
IN
)
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 ADP199 includes circuitry that has a
typical 1 ms turn-on delay, and a controlled rise time to limit the
V
IN
inrush current. As shown in Figure 34 and Figure 35, the turn-
on delay is nearly independent of the input voltage.