ADP171-BL1-EVZ Analog Devices Inc, ADP171-BL1-EVZ Datasheet - Page 13

• Manufacturer Part Number: ADP171-BL1-EVZ
• Description: Blank ADISimPower Eval ADP171
• Manufacturer: Analog Devices Inc

Specifications of ADP171-BL1-EVZ

• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

In this example, the worst-case temperature coefficient
(TEMPCO) over −40°C to +85°C is assumed to be 15% for an
X5R dielectric. The tolerance of the capacitor (TOL) is assumed
to be 10%, and C
Substituting these values in Equation 1 yields
Therefore, the capacitor chosen in this example meets the
minimum capacitance requirement of the LDO over temper-
ature and tolerance at the chosen output voltage.
To guarantee the performance of the ADP170/ADP171, it is
imperative that the effects of dc bias, temperature, and toler-
ances on the behavior of the capacitors are evaluated for each
application.
UNDERVOLTAGE LOCKOUT
The ADP170/ADP171 have an internal undervoltage lockout
circuit that disables all inputs and the output when the input
voltage is less than approximately 1.2 V. This ensures that the
ADP170/ADP171 inputs and the output behave in a predictable
manner during power-up.
ENABLE FEATURE
The ADP170/ADP171 use the EN pin to enable and disable the
VOUT pin under normal operating conditions. As shown in
Figure 30, 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.
As shown in Figure 30, the EN pin has hysteresis built in. This
prevents on/off oscillations that can occur due to noise on the
EN pin as it passes through the threshold points.
C
EFF
3.5
3.0
2.5
2.0
1.5
1.0
0.5
0
= 0.94 μF × (1 − 0.15) × (1 − 0.1) = 0.719 μF
0
Figure 30. ADP170/ADP171 Typical EN Pin Operation
0.2
BIAS
is 0.94 μF at 1.8 V, as shown in Figure 29.
0.4
0.6
V
0.8
EN
1.0
1.2
1.4
1.6
Rev. B | Page 13 of 20
The EN pin active/inactive thresholds are derived from the VIN
voltage. Therefore, these thresholds vary with changing input
voltage. Figure 31 shows typical EN active/inactive thresholds
when the input voltage varies from 1.6 V to 3.6 V.
The ADP170/ADP171 utilize an internal soft start to limit the
inrush current when the output is enabled. The start-up time
for the 1.8 V option is approximately 120 μs from the time the
EN active threshold is crossed to when the output reaches 90%
of its final value. As shown in Figure 32, the start-up time is
dependent on the output voltage setting.
1
2
1.2
1.1
1.0
0.9
0.8
0.7
0.6
0.5
0.4
CH1
Figure 31. Typical EN Pin Thresholds vs. Input Voltage
1.00V
Figure 32. Typical Start-Up Time
CH2 1.00V
EN
EN INACTIVE
B
V
W
EN ACTIVE
IN
(V)
M20.0µs
V
T
OUT
ADP170/ADP171
79.8000µs
V
= 0.8V
OUT
V
OUT
= 3.0V
A CH1
= 1.8V
2.72V