RTC Current Consumption - Revision 2 Silicon

Byron Loader

Other Parts Discussed in Thread: AM3352

Hi Guys,

I'm trying to determine if it is possible to use a Super-Cap for the Real Time Clock on the AM3352 Revision B silicon. The datasheet still references a maximum current of 5mA and no typical value. Revision A had a typical value of approx 300-400uA. Has anyone done any power measurements for the VDD_RTC on Revision 2 silicon.

Best regards

Byron

over 12 years ago

0 Biser Gatchev-XID over 12 years ago

TI__Guru**** 393215 points

Hi Byron,

No official data yet.

0 Byron Loader over 12 years ago in reply to Biser Gatchev-XID

Prodigy 140 points

Ive just found a link to another post "AM335x B silicon revision 2.1 RTC power consumption" which claims that the port uses 40uW of power.

Looks like I will be verifying this figure on my prototype.

0 Rick Brower over 11 years ago in reply to Byron Loader

Prodigy 130 points

DId anyone ever determine typical RTC power consumption for this series processor? Thanks.

0 Biser Gatchev-XID over 11 years ago in reply to Rick Brower

TI__Guru**** 393215 points

Hi Rick,

Please check this wiki: http://processors.wiki.ti.com/index.php/AM335x_Power_Consumption_Summary. The measurements have been updated for Rev.2.X processors.

0 AFM over 11 years ago in reply to Biser Gatchev-XID

Intellectual 560 points

Hi,

on my custom board, i m measuring about 50uA when RTC-only mode. on the wiki it is indicated that VRTC should be about 20uA. on pmic it's about 10uA on backup state : so let's say 30uA. how can resolve the difference of 20uA between 50uA and 30uA ?

thanks

0 Biser Gatchev-XID over 11 years ago in reply to AFM

TI__Guru**** 393215 points

Sorry, I cannot debug this issue based only on the information you provide.

0 AFM over 11 years ago in reply to Biser Gatchev-XID

Intellectual 560 points

hi,

we are using TPS65910A3 + AM3352B for custom board with backup battery for VRTC.

like described in http://processors.wiki.ti.com/index.php/AM335x_Schematic_Checklist, we have also :

VDDS_RTC - tied to VRTC LDO of PMIC

CAP_VDD_RTC - 1 uF decoupling capacitor to GND.

RTC_KALDO_ENn - tied to GND

RTC_PWRONRSTn - 1.8 V RTC power on reset.

EXT_WAKEUP tied to GND

PMIC_POWER_EN as input for PMIC

when the main power is off, the VRTC is maintained using ldo of PMIC via the backup battery.

in this situation, we have measured about 50uA as consumption when only VRTC is supplied.

regards,

0 Biser Gatchev-XID over 11 years ago in reply to AFM

TI__Guru**** 393215 points

Do you have a 10kOhm pulldown on RTC_KALDO_ENn or is it directly tied to GND? What is your RTC_PWRONRSTn reset schematic circuit?

0 AFM over 11 years ago in reply to Biser Gatchev-XID

Intellectual 560 points

The RTC_KLDO_ENn with 10k pulldown and the RTC_PWRONRST is like the StarterKit circuit.

0 Biser Gatchev-XID over 11 years ago in reply to AFM

TI__Guru**** 393215 points

If it's the same like the Starter Kit RTC reset circuit you will notice that there is a 100kOhm pulldown resistor on RTC_PORZ. 1.8V / 100 000 = 18uA, which would account for most of your missing current.

0 Chandrashekar Ishwaramangala Ganeshrao over 11 years ago in reply to Biser Gatchev-XID

TI__Intellectual 2370 points

Biser,

What is the typical current consumption on the VDD_RTC pin on AM335x device ?

The performance numbers mentioned about 0.79mW ? is this the one right data.

What is the recommendation on RTC , if the customer wants to use a backup a battery [3v coin cell] during power failure for timing keping ?

0 Biser Gatchev-XID over 11 years ago in reply to Chandrashekar Ishwaramangala Ganeshrao

TI__Guru**** 393215 points

Hi Chandra,

The data can be seen here: http://processors.wiki.ti.com/index.php/AM335x_Power_Consumption_Summary#RTC-Only .

My personal opinion is that an external RTC will provide a much longer battery life.

Processors

Processors forum

RTC Current Consumption - Revision 2 Silicon