Power Interface Forum - Recent Threads

TPS2501 Rilim resistor is not functioning and power up glitch. Urgent

John Wiemeyer — Fri, 24 May 2013 00:29:12 GMT

Need some technical support on the TI TPS2501. We have our prototype on the lab bench and we’re having trouble in 2 areas. See attached schematic.

First, Rilim

the Rilim resistor is not functioning and we don’t understand why. We’re using a 121K ohm resistor, which calculates to an iosmin of 150mA and iosmax of 319mA. Yet we pull 450mA and it *still* doesn’t FAULT#.

Second, a power up glitch

We have a 150uF tantalum on the output (as required by USB spec), and when we turn on the output switch, it really pulls a ton of power from the source and glitches the Vin so badly that we get RESETs. In the scope plots (attached) you can see :

YELLOW is the input voltage from the power supply (a lab bench very good one)
GREEN is the output of our 3.3V switcher (a very good one)
BLUE is our reset line
PINK is the +5V_USBH output of the TPS2501.

Notice that when the USBEN is turned on, we see the “lights dim” – a large current draw from the source supply while the 150uF cap charges.

This circuit has no USB load. Adding load does not change the “glitch” much.

The question is simple. is there ANY way to mitigate this glitch? We’ve tried increasing input caps to no avail. The result of this glitch (ie non-soft-start) is that we cannot run our board down below about 4.5V Vin or else all the reset circuitry is tripped post 3.3V.

just for clarification, we took the first scope capture from the TPS2501-EVM to confirm that the glitch was not just present on our board and was generated by the TPS2501. The EVM has a 470uF micro on Vin and the glitch shows up when we enable the USB switch with the boost enabled but also shows if we keep the USB switch enabled and enable the booster.

Thanks for your help.

John Wiemeyer

(Please visit the site to view this file)

Detecting device being charged has been unplugged using TPS2511

Glenn Zelniker — Fri, 24 May 2013 18:51:47 GMT

I have the TPS2511 set up for 10W mode and I'd like to be able to detect when the device being powered or charged has been disconnected. I have found a workable solution already: namely, I use a micro w/ ADC to look at the level on the D+ and D- lines and I've identified a state that always and uniquely corresponds to a no-load condition. The problem is that some devices cause the TPS2511 to take a while (e.g., 15 seconds) for D+ and D- to return to that state when the device gets disconnected. An iPhone only takes a second or two; an older BlackBerry Pearl takes a full 15 seconds.

I have seen some newer chips (e.g., TPS2546) that have status pins that seem to indicate a load-disconnected condition, although I can't really infer from the datasheet if this means the device is truly disconnected or if it is merely finished charging. For my application, I actually need to know, unambiguously, that the phone or tablet has been physically disconnected from the charger.

TPS23756 design

ILS — Thu, 23 May 2013 10:39:48 GMT

(Please visit the site to view this file)

There is a design number PMP6584 at TI website (slur490.pdf)

It is TPS23756 PoE Dc-DC with 8V 3A output

Is there any way to trim down the voltage to 6.5V-7V?

How it will affect the performance?

TPS2492PW Overvoltage Input (OV)

Vladimir Nohava — Tue, 21 May 2013 18:33:41 GMT

The OV internal reference (VOV_H - Threshold voltage) is affected by which parameters? (1.31Vmin 1.35Vtyp 1.39Vmax)

Does these parameters include temperature and lot-to-lot tolerance?

If temperature is involved, in which direction does it effect the min/max values? (cold = towards 1.31V or 1.39V?)

Thanks

Vlad

LM3481 shut down not working

Rob vreden — Mon, 10 Dec 2012 11:26:43 GMT

Hello, I have the LM3481 as an step up regulator in use. I have used webench to calculate the values of the components. The regulator works fine. It steps up from 8-35 volts input and has an output of 24 volts at 1 amp.

The issue I have is that I want to shut it off when current reaches maximum. I have an high side curent sensor for that. The output shuts the fet as suggested in the datasheet.

At this moment I have an 34,8k from pin 6 to gnd. When connected to gnd, the regulator gives 24 volt at 1 amp max. all works ok.

But when I connect this 34,8k to the 5Volt, it does not shut off the regulator.

According the data sheet; if this pin is made high( >1,3 Volt) it shuts the regulator. Well, it does not in my scheme. it lowers the Voltage from 24 to 18 Volts, but does not shut. I use 5 Volts to shut it. I measure 5 Volts at the IC. but the IC does not shut.

what am I dooing wrong?

regards,

rob van vreden

PoE PSE Isolated DCDC Converter 12V/48V

Christian Merk — Thu, 16 May 2013 13:05:01 GMT

Hi,

i need a power supply for a PSE (802.3af) with 4 Ports (~60W). If i'm right, the power supply and the

PSE part has to be isolated to the rest of the cuircit (NIC etc..). 12V are available, but i need ~48V so i have

to design a DCDC boost converter, but i can't find any ANs oder reference designs for isolated converters (except PMP7899).

Are there any information, especially about dimensioning the transformer, which can help me to design it?

I thought this would be a standard application, but it's hard to find information about this kind of converter.

Thanks in advance,

Chris

TPS2544/ TPS2546 not working with Samsung

Bill Tischer — Tue, 14 May 2013 16:30:00 GMT

I'm testing the new TPS2544 and TPS2546 with a Samsung Galaxy Tab 2 which uses the 1.25-volt D+/D- sensing protocol and I'm not able to get it to charge. Also doing the same thing for the Galaxy Note -- it too does not charge. Apple products charge OK so I know the connections on the board are OK. Any ideas?

Power switch

Pes — Wed, 15 May 2013 17:11:10 GMT

Hi,

   I' m looking for a power switch which can supply from a first voltage if present (3.3V with USB connected) or from a second voltage (battery) if not.
   The circuit must supply 300mA from the first or the second voltage.
   I would like to have a low quiscent current <1µA if possible.

   from a main 300mA from one Voltage 3.3V if USB is present) and 300mA or from another. If the first Voltage (from USB) is present. The switch can integrate or no an LDO function for the first Voltage.

   Do you have such a integrated circuit for me?

   Thank you

TPS2511 charging Inquiries

Chee Kang Lim — Thu, 16 May 2013 06:05:51 GMT

Thank you.

Best Regards,

CK - Serial Microelectronics TI FAE

TPS2010A Not limiting the output current

Nandakumar MReddy — Wed, 15 May 2013 11:41:32 GMT

Hi,

We are using TPS2010A in our application.

An regulated 5v@1A input is given to TPS2010A and we are expecting the load to limit for 5V@ 200mA even if i connect more than 200mA load.

But in our case the load switch is not limiting the output current. We see that if the load exceeds 200mA the output of TPS2010A also increases accordingly.

We have observed that output of TPS2010A was sourcing upto 600mA when i connect higher load(say 5V@1Ah load)

Please let us know why this is happening so. I need to limit the output current to 200mA.

Regards

Nanda Kumar M

TPS2421 Inrush

PAN-M — Tue, 14 May 2013 11:48:45 GMT

There is a 10ns cycle ringing to our power supply input in connect timing.

If I was using the TPS2421, this inrush waveform does not go out to the output?

Regards,

PAN-M

If TPS23754 can power up to 33W??

Chen Bogey — Fri, 10 May 2013 09:20:38 GMT

Dear Sir

Good days,

May we check if TPS23754 can power up to 33W(12V/2.75A)??due to spec show power up to 30W.

If yes, may we direct use TPS23754EVM-383 to driver, is any thing to change?

Best regards,

Bogey

TPS27081A Output Votage

HIDE — Wed, 01 May 2013 07:54:06 GMT

Hi,

I have a question about output voltage on TPS27081A.

It was measured 0.8V output voltage continuously during enable off. Is that correct behave on this device?

(I guess output voltage should keep 0V during enable off.)

Best Regards,

Hide

LM5060 overcurrent issue

Philipp Pfaffeneder1 — Tue, 07 May 2013 10:05:00 GMT

Hello guys,

I have the LM5060 device in use in several projects and want to use the over current protection, too.

Due to an error on one of our PCBs the power path was shorted, but also the MOSFET, a SQM120N04 with 120A,

was defect, too, despite the over current protection was 30A (Rsen = 3kOhms) and the time was 200mA (Ct = 1µF).

Then I researched this phenomenon and I found, that even the current protection is about 1A, a hard short causes a

periodic reactivation of the FET(driver). Only if I connect a 10Ohm resistor at 26V (appx. 2,6A) the protection latches

till supply toggle or similar. How could this be? And moreover, how can I get a working overcurrent protection or how

I have to configure the parameters Rsen/Ct? Hope someone could help me :-)

Kind regards,

Philipp PFaffeneder

TPS2490 troubleshooting

DURIEUX Xavier — Thu, 02 May 2013 06:53:08 GMT

I have some trouble with TPS2490 hotswap controler. The design is made to switch off in case of a short circuit at power output. The MosFET is a SUP90N10. Power limit is set at 60W, current limit at 14A, timer at 150ms. Even with the MosFET SOA respected, power is correctly limited during 40-60ms. After this delay appear a "switch mode behaviour", where power is still limited at its nominal value, but with high surge current. Can it be a too high gate series resistance ? Is there any other parameter to adjust ?

Thank you

USB Charging Detectors TPS2540, TPS2541, TPS2543, TPS2511

David Shenker — Tue, 30 Apr 2013 03:00:24 GMT

Hello All,

Can a compatibility list provided for the TPS2540, TPS2541, TPS2543, TPS2511?

I am designing a USB charger, and need to determine which device will provide the largest
degree of compatibility to mobile devices. The charger is a DCP device.

Thanks.

TPS23750 Switcher Minimum ON Time

Martin Patoka — Wed, 01 May 2013 13:48:08 GMT

"What is the minimum ON time for the PWM in the TPS23750? A customer is designing a PoE to 3.1V/850mA buck and wants to know this for a worst case analysis."

See top of P19. With correct control of the COMP pin, the switcher can be turned off (on time = 0). Once there is sufficient voltage on COMP to reset the switch control, the minimum on time is set by the internal delay + blanking time per the tblnk spec in the Electrical Characteristics table (note several choices).

LM5070 PoE PD_3.3V schematic review?

Eric Kim38719 — Fri, 26 Apr 2013 16:44:07 GMT

Hi,

Can I get attached LM5070 schematic review and advice?

It is used for PoE PD_3.3V of CCTV.

I referred Snva104.pdf(AN-1358 LM5070 (AE)) and Figure9. Non-Isolated solution in Page8.

(Output Voltage : 3.3V used)

I think almost same with Figure9. Non-Isolated solution in Page8.

(Please visit the site to view this file)

thanks,

TPS2350 transient limits and handling

Kim Olsen — Wed, 24 Apr 2013 14:33:46 GMT

2 issues, both are transient related and have show up during product testing.

1) Please confirm that the limit for voltage between SOURCE and RTN is 100V for the absolute maximum. The datasheet specifies this for the SENSE pin which is connected through a low value resistor (0.01 ohm in the application schematic) so SOURCE should track very close to SENSE.

2) The problem that we are seeing is that when we apply a Common Mode transient to the frame ground of our product, we see greater than -100V between SOURCE and RTN (as much as -110V). This transient is coupled through D1 (from application drawing on page 1 of datasheet) which is actually reversed biased during the transient. The reverse biased current through D1 is on the order of 250uA (1pF X 500V/2uS = 250uA). This current pulls the voltage between RTN to SOURCE from a nominal -50V down to -110V which exceeds the TPS2350 absolute maximum ratings. We think a simple solution to this problem may be to place a .01uF capacitor between SOURCE and RTN. The capacitor divider between the 1000pF cap and the ~1pF reversed biased capacitance of D1 should reduce the coupled transient to virtually nothing.

We need to know if this is a valid solution or if a better one can be proposed.

TPS2350 / SWITCHING BETWEEN POWER SUPPLIES

Ran Feldman — Tue, 30 Apr 2013 09:07:23 GMT

Hi,

Our customer is using the TPS2350 and encountered some problems:

Attached are the schematics (load(25W) is located on other pages) based on SLUA468 application report.

(Please visit the site to view this file)(Please visit the site to view this file)

The Customer has 2 power supplies, A (Primary) and B (Secondary) and they want them both to be redundant. Here is the description of the phenomenon:

Both A and B power supplies are ON. Channel A is supplying current (Va>Vb). Decreasing A’s voltage (or increasing B’s voltage) and when the difference between them is about 0.5V(Vb-Va=0.5V) channel B takes over and supplies current. All works fine.

Both A and B power supplies are ON. Channel B Voltage is higher than A’s (Vb>Va), Decreasing voltage B(or increase voltage A), A doest take control, nothing happens if even Va significantly exceeds Vb.the customer checked pins 14 and 13 of the chip (VINA and VINB) and found that although Ch A voltage decreased, VINA follow to VINB(with difference 300mV), this is not enough for the comparator to switch to channel A. This deadlock is permanent: channel A cannot take control over load. If the customer switched off channel B, channel A does take control, but only after 1-2 Sec during which the voltage on load dropped down to zero. This is unacceptable for the design.

The customer tried a separated power supplies, or short connecting RTN_A_F and RTN_B_F signals. Nothing changed.

In summary, the customer wants both supplies to switch between them on one of them encounters a problem.

Please advice,

Thanks

Regarding TPS27082's on/off operation

yunsong sim — Fri, 26 Apr 2013 05:09:56 GMT

Hi, I want to use TPS27082 as a swtch for my load which would be 5V/2A.

And I also want to this load switch with magnetic sw (lead sw) as a toggle mode. So I integrated CD4013B for this function with this load sw. I attached the schematic for this circuit.

But the problem is that this on/off pin(no,5 of TPS27802) doesn’t work with CD4013.

After removing R9(0ohm, jumper), CD4013’s output is working well which means that whenever the lead sw on/off, pin13’s output is toggled well between 0V and 5V(VDD voltage). But with R9 it doesn’t work and always TPS27082's output remains on-stage.When I read its datasheet, I think TPs27082’s on/off pin would work well with CD4013’s output, is it wrong?

Where should I check for this problem?

(Please visit the site to view this file)

TPS23753AEVM-001

Gary Case — Mon, 29 Apr 2013 13:55:49 GMT

We ran a Conducted Emissions scan on the evaluation board and did not get as good results as what you provide in your documentation. We get a peak at the switching frequency of 262 kHz of 74 dBuV but in your literature the same peak is well below 68 dBuV. The rest of the scan results are very similar to that in the literature, it is just the fundamental peak. All we are doing is putting a resistive load on the output. I would like to learn more on how TI achieved their results or if you have any comments on ours. I tried to paste the scan results in this email but was unsuccessful.

Regards

Gary Case

TPS2543 - Can TPS2543 support iPad(2.4A)?

hideto kanemaru — Mon, 22 Apr 2013 10:53:11 GMT

Hi,

TPS2543 supports iPad(2A), can TPS2543 support iPad(2.4A)?

(Will "Divider 2" allow charging iPad devices at 2.4A?)

"iPad(2.4A) = 5.2V/2.4A" is a new standard of Apple Inc.

Regards,

Kanemaru

TPS2511 – Does TPS2511 not have Forced Vividre1 function such as TPS2543?

hideto kanemaru — Thu, 25 Apr 2013 18:01:56 GMT

Hi,

Does TPS2511 not have Forced Vividre1 function such as TPS2543?

Is Divider mode of tps2511 automatically changed(Divider1 -> Divider2)?

Regards,

Kanemaru

TPS2543's Device Control Pin

Tsuguhiko Asai — Wed, 24 Apr 2013 01:48:30 GMT

Dear All,

Please teach us setting of Device Control Pin of TPS2543.

When customer use DCP_Auto Mode, the setting of each CTL Pin is follows.

(CTL1,CTL2,CTL3)=(0,1,1)

(CTL1,CTL2,CTL3)=(0,0,1)

Please teach difference between (0,1,1) and (0,1,1).

Best Regards,

Tsuguhiko Asai