AND8028 Datasheet, PDF (2/4 Pages) ON Semiconductor – Precision Sub-One Volt 1.7 Ampere Output LDO

V_out
C2
100 m
R1
1.5 k
R2
4.3 k
AND8028/D
Q1 MBT35200MT1
C4
1n
R6
R3
R4
1k
18
10
NCP100
U1
Q2 MBT3904
C3
1m
D1
MRA4003T3
R5
300
V_in
C1
100 m
Figure 1. Circuit Schematic for 0.9 Volt 1.7 Ampere LDO
RESULTS
Utilizing the circuit in Figure 1, layout in Figure 3 and
values in Table 1, the output voltage varies 40 millivolts
between 1.5 volts to 3.0 volts and 0 amperes to 1.7 amperes
for an output voltage centered at 0.945 volts, which equates
to a +/– 2.5 % variation for load and line. The voltage droop
due to load transient is small as seen in Figure 2. If R1 is
varied to change the output voltage to 1.8 volts, the
minimum drop out voltage is 34 millivolts under light load
conditions and 230 millivolts for 1.7 amperes. The
minimum input voltage to operate of the circuit in Figure 1
is 1.42 volts for 1.7 amperes and 1.37 volts for 0.5 amperes.
As discussed previously, the operating range of this circuit
can vary depending upon R3.
V_out: 200 mV/div
I_out: 0.5 A/div
Time Scale: 100 us/div
Figure 2. Load Transient for 1.8 Volts In and Load
from 0.5 Amperes to 1.5 Amperes
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