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BQ76940: Isolation in communication in BMS using BQ76940

November 15, 2019, 9:47 am
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Part Number: BQ76940

Hi,

I'm designing a BMS for a scooter based on the bq76940 and ‎bq34z100-G1 ICs + high side fet driving. I studied very consciously the TIDA-010030 ref design. In my requirements, I need to provide an isolated 3V3 UART. I also need to provide an aux voltage of 5VDC to host. Here, HOST is the board mounted in the scooter and contains, besides other electronics, the brushless DC motor driver, speed and braking control, an IoT transreceiver, etc. 

Because of current requirements in the supplied aux voltage to host, I'll use the SN6505 (1A out max) for driving a transformer, generating 5V_AUX_ISOLATED and GND_ISOLATED from BMS to HOST.

For the tx, rx lines, I'll use popular opto-couplers part.

The total signals to be interfaced to HOST are: 5V_AUX_ISOLATED, GND_ISOLATED, RX_ISOLATED, TX_ISOLATED plus PACK+ and PACK-

My question is:

I don't understand why opto-isolation is beneficial in this situation, considering that the motor driver is using PACK- and PACK+, breaking the isolation. So, the motor-driver is referenced to GND_ISOLATED, but the low side fets for driving the motor are referenced to PACK-. Does it make sense my concern?

Thanks a lot

Kind regards,

Sebastian

 

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UCD90120A: After clearing "(EAh) LOGGED_FAULTS", UCD don't log faults any more

November 15, 2019, 10:33 am
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Part Number: UCD90120A

Dear sir,
For the register: (EAh) LOGGED_FAULTS, base on documentation it could be clear after PMBus perform a Block_Write with 0 on it.
But after clear, UCD do not log faults any more even AC power cycle. Do you have any idea of this situation?
Here is our log shows each byte in EAh are all ZERO.
root@ubuntu:~# ipmitool i2c bus=2 0x68 0xf 0xea
 0e 00 00 00 00 00 00 00 00 00 00 00 00 00 00
Thanks!
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TPS54326: Stability with 2.2 uH inductor for 0.9V generation

November 15, 2019, 10:50 am
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Part Number: TPS54326

Hi team,

My customer wants to use 2.2uH inductor for 0.9V Vout from 12V Vin @ 2 A load setup, in order to get more smaller ripple. Then I got following two questions from them. Could you give me any advises?

1. Can you tell me if you have any concerns(like stability issue) and estimated power supply characteristics changes when changing to 2.2uH?

2. If there is a issue on stability, is it possible to solve that  by changing component parameters like the feedback resistance?

[Their current setup]
Vin : 12V
Vout : 0.9V
Load : 2A
Inductor : 1.5uH
Cout : 44uF(22uF + 22uF)

In current setup, they referred to following TI recommendation but the output ripple was a little bit bigger than they estimated. So they want to get it smaller with no design change. They could got smaller ripple with larger Cout but it needs layout change.

　The inductor and capacitor selected for the output filter must be selected so that the double pole

　of Equation 5 is located below the high frequency zero but close enough that the phase boost provided by the

　high frequency zero provides adequate phase margin for a stable circuit.

　To meet this requirement use thevalues recommended in Table 1.

 

Regards,

Takashi Onawa

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EM1402EVM: EM1402EVM

November 15, 2019, 11:14 am
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Part Number: EM1402EVM

Hi,

 I'm using the EM1402EVM together with LAUNCHXL-TMS57004 and I have some questions about the ACB. I attach two images of the GUI for more information.

In the GUI, when the ACB is enable and the energy exchange is in progress, the ACB affects the cell that needs to be balance(CELL 3) and the two cells that are next to the cell 3.  Cell 2 and Cell 4. Why this happend? This always happend when the ACB is enable. I don't mean that it is a fault, I just want to know why this happens.

Thanks

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LM74670-Q1: Avoiding a diode drop on full bridge rectifier?

November 15, 2019, 12:24 pm
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Part Number: LM74670-Q1

Hello team,

Are you able to rotate the fet's on the second half of this rectifier to avoid a diode drop of the fets?

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TPS54320: Max current limit/max minimum pulse width

November 15, 2019, 1:27 pm
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Part Number: TPS54320

Hello,

The datasheet does not have a specd max for Current Limit or Minimum Pulse Width. Is this info available?

Thanks,

Michael

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BQ25606: Which Current Limit has higher authority?

November 15, 2019, 1:41 pm
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Part Number: BQ25606

Hello,

I am curious about how ILIM works with adapter detection. For example, if I set my input current to 1.8A, but the detection pins detect a charger capable of 2.4A, what will IINDPM be?

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LM5022: UVLO input leakage spec and voltage clamping

November 15, 2019, 5:01 pm
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Part Number: LM5022

Hello,

The LM5022 datasheet specifies the abs max voltage level at the UVLO input as 7V.

There is no max value specified.

In the customer's application the input working voltage is 10.5V to 60V.

To ensure this functionality, a 105K + 14k7 UVLO voltage divider was chosen.
At 60Vin the UVLO voltage calculates to 7.37V nominal, potentially higher with 1% tolerance resistors.


I would expect that at that voltage level the hysteresis current generator is no longer functional (saturated).
However, the DC probing of the UVLO pin reads 6.25V which i cannot explain.

1. what is the UVLO maximum allowable voltage?
2. what is the UVLO input current leakage?
3. does the UVLO input have clamping diodes to the comparator's internal bias?
4. if clamping is present, what is allowable current into the diode?
5.if no clamping occurs, is external clamping circuitry needed and what woud be recommended as a low cost solution - a DZ has significant leakage over temp itself, a 431 clamp adds cost and parts count.

there is no app note in the datasheet for this in-spec use case

Thank you.

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BQ25619: Vsys selection

November 16, 2019, 3:27 am
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Part Number: BQ25619


How can I adjust the system voltage of the buck. I just found the upper and lower limits in the datasheet but not how to adjust the system voltage it self. I would like to have a system voltage not higher than 3.6 volts.

Regards Raphael

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BQ25618: BQ25619

November 15, 2019, 6:50 pm
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Part Number: BQ25618

I'm studying on earbuds pin and charging, and I use BQ25618 for earbuds charging case. However, I have no idea for chip on earbuds. My problem is not know some popular switching mode bucks in earbuds, which is compatible with BQ25618. Please help me to solve my problem. Have a good day and thank you so much. 

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LMR23630: Looking for Higher Input Voltage Rated Part with Same Pinout

November 16, 2019, 7:06 am
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Part Number: LMR23630

I have a board designed with the LMR23630ADDA but after assembling and looking at tolerances I realized that my input voltage can be greater than 36V. The input voltage comes from a half wave rectified 24VAC transformer which is (24VAC * pi *.45) ~34VDC but in reality the transformer outputs 27VAC yielding ~38VDC plus ripple. I believe that this is causing the regulator to blow.

I took a look but could not find a regulator with the same SOIC-8 pinout. It seems that I was unlucky in choosing this part, not only because of my oversight on the input voltage rating but also because it seems the pinout of this part is different than almost every other part that I looked at.

I'm hoping maybe I just overlooked something and that someone who knows the product line knows another part that I can drop in. The regulator will be generating 3.3V and probably close to 500mA 

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UCC25230: Zener diode COMP pin

November 16, 2019, 8:21 am
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Part Number: UCC25230

Hi,

Figure 9 in UCC25230 datasheet which depicts the typical application have D2 Zener diode connected to COMP pin.

 


What is the role of the diode ? Is it mandatory ? UCC25230 Bias Power-Supply Design Review uses 3.9V Zener, what is the main reason to use this diode?

UCC25230 datasheet does not describe and explain D2 function.

Thanks.

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BQ51013: Circuit cycles - does not give a steady output

November 16, 2019, 11:03 am
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Part Number: BQ51013

Can anyone help or suggest a test regime please?

The attached PDF shows the power supply circuit of my project . The design is taken from the component data sheets with values calculated against the coil inductance Ls = 12u3H  (quoted) and Ls' = 16u5H (extrapolated from other data).

I would anticipate a steady output at [OUT] when the coil is on the charger, regardless of load. I have tested with both a 'Chinese' wireless charger and a Samsung phone charger. The results are the same.

With a LiPo (open voltage 3v73) connected at [V_BATT], or no battery connected, I see LED_3 (!CHG_1) and LED_1 (!CHG) flash on momentarily, then after a short delay, repeat.

If I connect a faulty LiPo (open voltage 2v93), I see the same as above, but in addition LED_2 (!PG) comes on momentarily after LED_1

Lipo capacity 600mAh (quoted)

(Please visit the site to view this file)

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LMZ31710EVM-001: Surge in input supply current for specific input voltage range

November 16, 2019, 5:58 am
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Part Number: LMZ31710EVM-001

Hello,

My application required an output voltage of 5.25 V from an input voltage that ranges from 6 to 8.4 volts. I am using the LMZ31710 EVM to produce an output voltage of 5.0 V ( Fsw select at 1.0MHz) to evaluate the module. I have swept the input voltage using a power supply and monitor the drawn input current. The nominal input current is ~4mA at 6V. As I gradually increase the input voltage, the input current suddenly increased to nearly 30 mA at 7 V and continues in this range up to 8 V and it then begins to decrease down to 6mA at 8.6 V. Is there an explanation for this current surge?

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BQ25120: Role of R27, 100K,

November 16, 2019, 6:33 am
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BQ2057W: Charge Controller compatible with 2s2p battery

November 16, 2019, 4:12 pm
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Part Number: BQ2057W

For a school project, part of our tasks include charging a lithium ion battery. The battery pack we have is an RRC 2057 2s2p and was wanting to check and see if I could use the bq2057w as a charge controller for a 2s2p battery. Am planning to design circuit based on figure 1, page 7 on the bq2057 datasheet. However, was planning on using a 62.5 mOhm resistor to set charging current at 2 A and a BDP 948 PNP transistor. 

Thanks for the help,

Ryan

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BQ34Z100-G1: How to test SOH function is working

November 16, 2019, 8:50 pm
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Part Number: BQ34Z100-G1

Hi,

I am having trouble getting SOH to show anything more than 100%.  I found an app guide that talks about adding 100 to 200 mOhm between the gauge and battery leads in order to simulate an increased ESR. After a full charge/discharge cycle, It was said that adding this ESR would change the SOH value.  I have tried adding 45mOhm and 100mOhm ESR with no success.

We have 4S2P configuration of LiFePo4.  The gas gauging we have so far looks very accurate.

Q1. Cycle count in the "Gas Gauging/State/Cycle Count" is still at zero.  Is this an indication that Qmax is not updating and therefore SOH is not updating?

Q2. What else would keep the SOH from updating?

Q3.  Is there a better way to test that this function is working correctly?

our *.gg.csv file is attached.

(Please visit the site to view this file)

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UCC28740: Design Calculator Secondary Current Question

November 16, 2019, 10:05 pm
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Part Number: UCC28740

Hello there,

I have opened up another form regarding this part, but I have a different question regarding the Design Calculator (Rev. B) tool (for the following transformer https://katalog.we-online.de/ctm/datasheet/750871011.pdf). I have finished filling out my design (attached) but I now notice on the "SCHEMATIC AND BoM" tab, that my peak secondary current is quite large, larger than any available transformer I have seen on DigiKey. My concern regarding this current is that the peak load current I have designed for is 1A, and the peak ripple current through the capacitor is 1.711A. By KCL, the maximum current the transformer should supply is 2.711A. Is there something within the design I am not considering here?

Many thanks in advance for your assistance.

Best Regards,

Chris

(Please visit the site to view this file)

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LMG1020: Selection of voltage regulator for gate driver power supply

November 17, 2019, 12:02 am
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Part Number: LMG1020

Hello, 

I am using lp38692sd-5.0/nopb voltage regulator for powering up LMG1020 in GaN based half bridge circuit.

While increasing the DC input voltage of half bridge, the Vgs for top switch is crossing the 6V(absolute maximum gate to source voltage).

So I would be thankful if you could suggest me some voltage regulators, in which the output voltage could be adjusted to 4/4.5/5V, so that I could have enough voltage margin for driving the gate of the top device. 

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UCD90320U: ADC reference voltage

November 17, 2019, 1:09 am
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Part Number: UCD90320U

When ADC reference voltage is not being used, can i keep it not connected?

Can i configure margin pins ,LGPO ,EN PINS as GPI PINS  in UCD90320U?

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