No LDO output on STEVAL-ISV020V1

[displaysgalore]

Hello,

I'm currently evaluating STEVAL-ISV020V1 using AN4397 and I'm not reading any voltages from both LDO outputs.

Here's my setup:

• PV_in: 2.6-2.7 V PV
• BATT: 5v supercap
• SW1 and SW2 enabled

I can confirm that the supercap is charging as STORE shows ~3.9-4V and BATT shows a gradually increasing voltage which reached >3.3V per my last test. SW1 and SW2 are enabled as both LDO_EN pins in CN3 show ~3.9-4V. UVP shows ~1.2-1.3V while EOC ~1V.

However, I am not reading any values at all in LDO1 and LDO2 in CN2. Am I missing something in my setup?

[Peter BENSCH]

Welcome @displaysgalore, to the community!

Please take a look at the data sheet of the SPV1050, where you will find, among other things, a note in table 1 that also applies to LDO2, stating that: :

LDO1_EN I If high, enables LDO1 (1.8V). Note that, independently of the LDO1_EN setting, the LDO1 is not active when the internal pass transistor is open.

A little further down in the same table, BATT_CONN is also listed:

Embedded pass transistor connection status pin (open drain):

• if low, it indicates that the pass transistor between the STORE and BATT pins is closed;
• if high, it indicates that the pass transistor between the STORE and BATT pins is open.

Unfortunately, the network at BAT_CONN (SPV1050, pin 8) is labelled somewhat confusingly in AN4397:

• fig 2 (schematics) refers to it as BATT_OK
• table 3 (CN2 connector) refers to it as BATT-CON, but mentions the pull-up required for its function

Hope that helps?

Regards
/Peter

[displaysgalore]

Hi Peter,

Thanks for looking into this. LDO2 has now turned on only when BATT reached the same value as STORE. As I understood from the datasheet, LDO2 should have already been active when the voltage difference between the two is equal to or less than UVP.

Now that LDO2 is active for me, I noticed that it drops from 3.3V to 1.4V upon loading. Could you help me understand why this is happening? It seems that the regulation is not good.