Datasheet

Data Sheet ADP194
Rev. A | Page 9 of 12
APPLICATIONS INFORMATION
GROUND CURRENT
The major source for ground current in the ADP194 is the 4 MΩ
pull-down resistor on the enable (EN) pin. Figure 16 shows
typical ground current when V
EN
= V
IN
and V
IN
varies from
1.1 V to 3.6 V.
0
1
2
3
4
5
6
7
10 100 1000
GROUND CURRENT (µA)
I
LOAD
(mA)
V
IN
= 1.1V
V
IN
= 1.5V
V
IN
= 1.8V
V
IN
= 2.1V
V
IN
= 2.4V
V
IN
= 2.7V
V
IN
= 3.0V
V
IN
= 3.3V
V
IN
= 3.6V
V
IN
= 1.3V
08629-116
Figure 16. Ground Current vs. Load Current, Different Input Voltages
As shown in Figure 17, 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)
GROUND CURRENT (µA)
V
OUT
= 1.8V
V
OUT
= 3.6V
08629-014
Figure 17. Typical Ground Current when V
EN
≠ V
IN
ENABLE FEATURE
The ADP194 uses the EN pin to enable and disable the VOUT
pin under normal operating conditions. As shown in Figure 18,
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)
08629-015
Figure 18. Typical EN Operation, V
IN
= 1.8 V
The EN input has built-in hysteresis, as shown in Figure 18.
The hysteresis prevents on/off oscillations that can occur due to
noise on the EN pin as V
EN
passes through the threshold points.
The EN input active/inactive thresholds derive from the V
IN
voltage; therefore, these thresholds vary with changing input
voltage. Figure 19 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
0
8629-016
Figure 19. Typical EN Pin Thresholds vs. Input Voltage, V
IN