Error in bq500211A Data Sheet / Question / DLP enabled

sven lehmann

Other Parts Discussed in Thread: BQ500211

Hi,

I found this information in the e2e community:

In the bq500211A Data Sheet (Dec 2012) Figure 8, “bq500211A Typical Low-Cost Application Diagram” pin 46 is shown grounded. Pin 46 is V_Sense which will sample the input voltage, when input voltage is low the DPL function will be active.

This pin should be connected to 3.3V for this application.

We regret the error and it will be corrected on the next data sheet revision.

Best Regards,

Bill Johns, Applications Engineer

bqTESLA Wireless Power Products

Texas Instruments Inc

Dallas, Texas

I recognised that I used a old datasheet for my schematic desgin. So V_Sense is tied to GND.

As far as I understand this enables the Dynamic Power Limiting.

In which way does this affect the circuit? How is DLP working?

I recognised that my own receiver has a poor performance. Therefore I measured the PMW frequencys.

The frequencys are ~200kHz and ar not dropping even if I connect a load (resistor) to the receiver.

Is this because the DLP is enabled?

As receiver I used the eval board bq51013EVM-725.

Regards

Sven

over 10 years ago

0 Bill Johns over 10 years ago

TI__Guru 65716 points

Dynamic Power Limiting (DPL) will look at input voltage level. When it drops to a point below 4.5V output power is reduced to bring the voltage back up. With pin 46 grounded input voltage is always below 4.5V and the DPL control is always active. Output power will be reduced to minimum and operating point set to max freq.

NOTE: Data sheet has been update.

0 sven lehmann over 10 years ago in reply to Bill Johns

Prodigy 90 points

I made some measurements at the bq500211evm-045.

Your answer was right. When the input voltage drops below something about 4.5V the PWM signal goes up to ~200kHz.

But I have one more question about the connection from V_Sense.

In the new datasheet V_Sense is connected to 3.3V. This is also under 4.5V.

As far as I understand this will also enable the DPL?

Why is V_Sense connected to 3.3V and not to VIN(5V)?

In the schematic of the bq500211evm-045 V_Sense (respectively V_IN / Pin 46) is connected to VIN (5V) over a 15,4k resistor.

For me it looks like the connection in the schematic of the bq500211evm-045 is the correct one.

Thanks

Regards

Sven

0 sven lehmann over 10 years ago in reply to sven lehmann

Prodigy 90 points

I made some more measurements at the bq500211evm-045 at the V_IN Pin (Pin 46 / measured at R11, C4).

The voltage at Pin 46 is 0,575V with an input voltage of 5V.

If the input voltage drops below ~4,31V the voltage at Pin 46 is somthing about ~0,495V and DPL is enabled.

So I think DPL is enabled when the voltage at V_Sense drops below 0,5V?

But as you proposed connecting V_Sense (Pin 46) directly to 3.3V, as connected in the new datasheet,

would also solve the problem.

Is that correct?

Regards

Sven

0 Bill Johns over 10 years ago in reply to sven lehmann

TI__Guru 65716 points

To Disable the DPL feature on the bq500211, pull pin 46 to 3.3V it will be high and unit cannot enter DPL.

To Enable the DPL feature use the recommended voltage divider network for pin 46. 76.8k / 10k with a 4.7nF filter capacitor.

Note the DPL feature requires I-Sense circuit to operate correctly.

See application circuit in the data sheet.

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Error in bq500211A Data Sheet / Question / DLP enabled