SPV1050 No Voltage at the LDO-Out Pins

[Joris2807]

Hi all,
I connected my SPV1050 chip as you can see in the picture and started to measure my circuit. It looks pretty good. I powered it up with 3.3V at IN_LV. And I can measure a voltage of about 2.416V at the STORE pin. And even the LDO2_EN pin got a 2.412V, but at the LDO2 pin there is nothing. Does anyone have any idea why this might be the case? Even when I connect the Battery, nothing changes.

[Peter BENSCH]

Welcome @Joris2807, to the community!

the datasheet of the SPV1050, section 6.1 says:

the pass transistor is closed once the (rising) voltage on the STORE pin triggers the over-voltage threshold VSTORE(EOC) (corresponding to VEOC > VBG)

The datasheet, table 1 says at LDO2_EN:

Note that, independently of the LDO2_EN setting, the LDO2 is not active when the internal pass transistor is open.

So if you measure a constant voltage of 2.415V at STORE, this is not enough to reach VEOC (with your values of R4, R5, R6: VEOC~4.21V) and thus close the pass transistor. It would then remain closed until the voltage at STORE has fallen below VUVP. However, as VEOC is obviously not reached, the pass transistor remains open and therefore LDO2 disabled and also pin BATT disconnected from STORE.

Regards
/Peter

[HUANG2]

Hi,
As the questioner mentioned, the voltage measured on the STORE pin is about 2.416V. Should we charge the battery at this time? What conditions can raise the voltage of STORE to VEOC.

Thank you for your reply and your help.

[Peter BENSCH]

Welcome @HUANG2, to the community!

Important is:

• the pass transistor remains open as long as VSTOREV does not reach the EOC threshold
• according to your schematic, VEOC with the resistors is about 4.21V
• only above VEOC is the internal path enabled, so that LDO2 can become active and the supply can be switched through accordingly

VSTORE only rises sufficiently if more energy is supplied to the storage capacitor or the STORE node than is drawn from it, for example by:

• The energy source at IN_LV must deliver enough power. If the source is too weak, VSTORE remains below the switching threshold.
• Enough charging time for the STORE capacitor to charge. Small currents or a high load prevent VEOC from being reached.
• If the load on LDO2 or the system is too high, the voltage on STORE is pulled down again.
• Missing or incorrect connection of BATT, STORE, LDO2_EN, external resistor dividers or protection paths can prevent charging. Also important: no unwanted leakage current or short circuit at the STORE node.

Check:

• measure VSTORE directly while the source at IN_LV is active
• vheck whether the STORE capacitor is correctly dimensioned
• reduce the load on LDO2 as a test
• check whether the circuit can really rise to VEOC ~4.21V

As long as VSTORE does not reach VEOC, LDO2 remains off. The battery is not meaningfully enabled in this state. Only when STORE rises above the EOC threshold through sufficient energy input does the internal pass transistor close.

Regards
/Peter