AND8028/D

http://onsemi.com

2

R1

1.5 k

R2

4.3 k

R4

10

R3

18

R6

1 k

C2

100

m

C1

100

m

C3

1

m

Q2 MBT3904

D1

MRA4003T3

R5

300

NCP100

U1

Q1 MBT35200MT1

C4

1 n

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.

Time Scale: 100 us/div

Figure 2. Load Transient for 1.8 Volts In and Load

from 0.5 Amperes to 1.5 Amperes