Programmable linear voltage regulator (such as LM317 or TL431) solver program for the HP 42S

for the HP 42S
AVR - Adjustable voltage regulator (such as LM317 or TL431) solver program / HP 42S

Circuit diagram (simplified)

Usage : [SOLVER] [AVR]

Variables to be used

Var Vo: Output voltage [V] (Vo > Vr * 1.0001)
Var Vr: Reference voltage [V] (Vr ≥ 0, default 1.25 V)
Var Iq: Adjustment pin current [A]
Var R1: Resistance [Ω] (R1 > 0, default 240 Ω) 
Var R2: Resistance [Ω] (R2 ≥ 0)

Program list

AVR - Rev.1.00 : Aug. 12 2011


00 { 104-Byte Prgm }
01 LBL "AVR"
02 MVAR "Vo"
03 MVAR "Vr"
04 MVAR "Iq"
05 MVAR "R1"
06 MVAR "R2"
07 XEQ 00
08 RCL "R2"
09 ENTER
10 RCL× "Iq"
11 X<>Y
12 RCL÷ "R1"
13 1
14 +
15 RCL× "Vr"
16 +
17 RCL- "Vo"
18 RTN
19 LBL 00
20 RCL "R1"
21 X≤0?
22 240
23 STO "R1"
24 RCL "Vr"
25 X≤0?
26 1.25
27 STO "Vr"
28 0.01
29 %
30 +
31 RCL "Vo"
32 X>Y?
33 RTN
34 X<>Y
35 STO "Vo"
36 RTN
37 .END.

Example

Input (LM317)	Input (TL431)
`Vo = 4.5 [V] Vr = 1.25 [V] Iq = 50E-6 [A] R1 = 240 [Ω] R2 = 240 [Ω] (to be solved)`	`Vo = 3.3 [V] Vr = 2.495 [V] Iq = 2E-6 [A] R1 = 10E3 [Ω] R2 = 10E3 [Ω] (to be solved)`
Output (LM317)	Output (TL431)
`x: 618.066561014E0`	`x: 3.20079522865E3`

DOWNLOAD

'AVR-1.0' (avr.raw, 107 byte, raw program file for the Free42)