BQ76PL536A-Q1: Too high sleep current consumption.

Jozef Augustín

Part Number: BQ76PL536A-Q1
Other Parts Discussed in Thread: BQ76PL536A, BQ76PL536

Hello

I built a prototype with BQ76PL536A-Q1. Everything works good, except sleep current. In the datasheet is written the sleep current value max 22uA. When I set IO_CONTROL[SLEEP] = 1 current consumption is 400uA.

Here is my initialization :

reg_write(BROADCAST_ADR, RESET, 0xA5); //broadcast reset
reg_write(BROADCAST_ADR, SHDW_CRTL, 0x27); //enable write to group3

reg_write(0x00, ADDRESS_CONTROL, 0x01); //set address

reg_write(0x01, CB_TIME, time_sec_max_63 & 0x3F); //set balance timer

reg_write(0x01,ADC_CONTROL,0x45); //set number of cell

reg_write(0x01, IO_CONTROL,0x04); //sleep

schematic is in attachment.

Can you help me with this problem?

Jozef Augustin

7178.Schematic.pdf

over 5 years ago

0 Leslie Marquez over 5 years ago

TI__Genius 9371 points

Hi Jozef,

Thank you for your question. Please confirm the following conditions are met when measuring sleep current, as defined in the "ICC sleep" spec conditions:

No load at REG50, SCLK_N, SDI_N, SDO_N, FAULT_N, CONV_N, DRDY_S, ALERT_N, TSx, AUX, or CBx;
CB_CTRL = 0;
CBT_CONTROL = 0;
CONV_H = 0 (not converting);
IO_CTRL[SLEEP] = 1

Also, can you please indicate where are you measuring the sleep current? My question is because "sleep current" should be the current going into BAT pins in the IC so it should be measured at that point. If you measure the current coming from the board supply, that supply is also providing power for all the other system level components you have on your board such as LEDs, FETs, etc. and hence the current will be higher.

Best regards,
Leslie

0 Jozef Augustín over 5 years ago in reply to Leslie Marquez

Prodigy 60 points

Hi Leslie

I checked everything and all conditions are met as you wrote above.

I am measuring sleep current on the top cell conection, but there are no other systems. Led and mosfet is disconected, there are no thermistors and control MCU is powered by USB.

I think that, higher sleep current causes leakage current through the communication bus. It is possible? Could you give me some recommendation for high impedance connection between MCU and BQ76PL536A?

Thank you
Jozef Augustin

0 Leslie Marquez over 5 years ago in reply to Jozef Augustín

TI__Genius 9371 points

Hi Jozef,

Please see reference schematic on page 47 of bq76PL536 datasheet for recommendation on connection between bq76PL536 and MCU:(www.ti.com/.../bq76pl536.pdf)

There could be several things that could be causing your sleep current to be higher. I summarize them below and also provide reference to where you can find more information in the datasheet:
* Data Ready: If doing conversion before entering sleep mode, DRDY_S remains asserted during SLEEP leading to extra current consumption. To avoid this, it is recommended to read the last result of a conversion before putting the device in SLEEP mode -> See page 17, "Data Ready" section
* REG50: This pin is an output. In your schematic I see you have a test point called "5V" connected to it. Is this "5V" test point connected to anything? -> See pages 47-50 for our recommended schematic
* REG50: REG50 should be disabled in SLEEP mode. Please check the voltage and current in REG50 pin when in SLEEP mode to confirm device is in correct state
* ALERT: When SLEEP mode is entered, the device sets the ALERT_STATUS[SLEEP] bit which causes the ALERT pin to be asserted. This will cause more current to be drawn until ALERT is cleared. To clear the ALERT, write 1 to ALERT_STATUS[SLEEP] followed by a 0 to ALERT_STATUS[SLEEP]. Verify that the ALERT was cleared also by measuring voltage on ALERT pin -> See page 26, "Sleep State Entry (bit set)" section
* IO_CONTROL[TS1(2)] bits: You must set these bits to 0 to minimize current drawn in sleep mode
* Current measurements on PCB: If after trying all of the above you still see the high current, I recommend to start measuring current directly into BAT pin and out of any output or I/O pin to determine where the extra current is going

Best regards,
Leslie

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BQ76PL536A-Q1: Too high sleep current consumption.