Part Number: TL432B-Q1
Hi expert,
My customer build LDO with TL432 in their automotive application and has ripple issue.
1. Test condition
(1) Build LDO circuity as shown in figure one
Figure 1
(2)Vin=6~7V, Vo=5V, Iout = 0~300mA
(3) R1=R2=Rfb, Imin=1 mA。
(4)NPN transistor has below characteristics
Figure 3
(5)Vin is supplied with DC source and digital load is in CC mode
2. Problem in testing
During testing, we fund different load condition and input voltage will cause large variation in output ripple. When decrease the resistance value of R3, output ripple becoming even larger. When empty load, Vout is 5V and no output ripple. Output ripple seems increase with load current. But, when load goes to heavy, ripple will drop again.
3. Testing results
(R1=R2=1k; R3=500Ω, CC load)
Vin/V |
Io/A |
Vo/V |
ΔVo/mV |
6 |
0.1 |
4.98 |
92 |
6.5 |
0.1 |
4.97 |
265 |
0.3 |
4.95 |
200 |
|
7 |
0.1 |
5.00 |
311 |
0.3 |
4.94 |
415 |
PS: Vo are all measured on digital load, actual LDO output is 0.01 to 0.02V high thean measured.
(R1=R2=1k; R3=333Ω, CC load)
Vin/V |
Io/A |
Vo/V |
ΔVo/mV |
6 |
0.1 |
4.98 |
146 |
6.5 |
0.1 |
4.99 |
285 |
0.3 |
4.94 |
366 |
|
7 |
0.1 |
5.00 |
313 |
0.3 |
4.96 |
499 |
PS: Vo are all measured on digital load, actual LDO output is 0.01 to 0.02V high thean measured.
(R1=R2=1k; R3=200Ω, CC load)
Vin/V |
Io/A |
Vo/V |
ΔVo/mV |
6 |
0.1 |
4.97 |
226 |
6.5 |
0.1 |
5.00 |
301 |
0.3 |
4.95 |
467 |
|
7 |
0.1 |
4.97 |
226 |
0.3 |
4.97 |
87 |
PS: Vo are all measured on digital load, actual LDO output is 0.01 to 0.02V high thean measured.
One waveform sample:
R1=R2=1k; R3=500Ω; Vin=6.5V, Io=0.1A; ΔVo=265mV
Thanks!
Sheldon