Datasheet

ADP190/ADP191 Data Sheet
Rev. E | Page 10 of 16
APPLICATIONS INFORMATION
GROUND CURRENT
The major source for ground current in the ADP190/ADP191 is
the 4 MΩ pull-down on the enable (EN) pin. Figure 19 shows
typical ground current when V
EN
= V
IN
and V
IN
varies from 1.1 V
to 3.6 V.
2.0
1.8
1.6
1.4
1.2
1.0
0.6
0.8
350300
250200
150100
500
LOAD (mA)
GROUND CURRENT (µA)
07874-013
V
IN
= 1.2V
V
IN
= 1.8V
V
IN
= 2.5V
V
IN
= 3.6V
Figure 19. Ground Current vs. Load Current
As shown in Figure 20, an increase in ground current can occur
when V
EN
≠ V
IN
. This is caused by the CMOS logic nature of the
level shift circuitry as it translates an EN signal ≥ 1.1 V to
a logic high. This increase is a function of the V
IN
− V
EN
delta.
14
12
10
8
6
4
2
0
3.50.1 0.3 0.5 0.7 0.9 1.1 1.3 1.5 1.7 1.9 2.1 2.3 2.5 2.7 3.33.12.9
V
EN
(V)
I
GND
(µA)
07874-014
V
OUT
= 1.8V
V
OUT
= 3.6V
Figure 20. Typical Ground Current when V
EN
≠ V
IN
ENABLE FEATURE
The ADP190/ADP191 use the EN pin to enable and disable the
VOUT pin under normal operating conditions. As shown in
Figure 21, when a rising voltage on EN crosses the active
threshold, VOUT turns on. When a falling voltage on EN
crosses the inactive threshold, VOUT turns off.
2.0
1.8
1.6
1.4
1.2
1.0
0.8
0.6
0.4
0.2
0
1.20 0.4 0.5 0.6 0.70.1 0.2 0.3 0.8 0.9 1.0 1.1
V
EN
(V)
V
OUT
(V)
07874-015
Figure 21. Typical EN Operation
As shown in Figure 21, the EN pin has built-in hysteresis. 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 VIN
voltage; therefore, these thresholds vary with changing input
voltage. Figure 22 shows typical EN active/inactive thresholds
when the input voltage varies from 1.1 V to 3.6 V.
1.15
1.05
0.95
0.85
0.75
0.65
0.55
0.45
0.35
3.60 1.20 1.35 1.50
1.65 1.80 1.95
2.10 2.25
2.40
2.55 2.70 2.85 3.00 3.15 3.30 3.45
V
IN
(V)
TYPICAL EN THRESHOLDS (V)
EN ACTIVE
EN INACTIVE
07874-016
Figure 22. Typical EN Pin Thresholds vs. Input Voltage, V
IN
TIMING
Turn -on delay is defined as the delta between the time that EN
reaches >1.1 V until VOUT rises to ~10% of its final value. The
ADP190/ADP191 include circuitry to set the typical 1.5 μs turn-
on delay at 3.6 V V
IN
to limit the V
IN
inrush current. As shown in
Figure 23, the turn-on delay is dependent on the input voltage.