Linear Regulators

TPS77001

Mathieu BREGEON — Thu, 12 Nov 2009 15:46:19 GMT

Hello,

I used the TPS77001 to generate 20 mA through one LED. So I put my LED between OUT and FB, and then a resistance around 60 Ohms between FB and the ground. I added an output capacitor of 10 uF (tantale). It worked well until I removed my LED.. now even if I put my LED back, it doesn't work anymore. So I think the TPS77001 was harmed when I removed my led, but I don't really understand the reason and how I could fix it. I want that I can remove my LED without turning off my voltage source.

Thanks for your help.

Regards

Mathieu

ps:It's the first time that I am using this TI community.

TPS71501 FB pin voltage

Kai-kin So — Wed, 11 Nov 2009 03:10:53 GMT

For TPS71501 adjustable voltage LDO regulator, the output voltage is set by a feedback of reference voltage to the FB pin.

The datasheet states that the operating output voltage is 1.2V to 15V.

I am wondering whether I can get rid of the resistor divider if I want the maximum output (15V).

I would like to know

1) the absolute voltage range of FB

2) what the output would be if FB is tied to GND. It first comes to me that Vout would be equal to Vin(<24V) but the datasheet specifies max Vout is 16.5V, so the regulator would be damaged for Vin>16.5V in this case?

Thanks.

linear reg

Bnovus — Tue, 24 Mar 2009 21:25:03 GMT

I need a linear regulator that I can adjust the voltage and the current limit. less than 1 amp, about 15 volts out 40 vdc in

LDO for a temperature sensor

Brennan — Thu, 30 Jul 2009 06:28:24 GMT

Hello.

I am looking for an LDO that consumes very, very low power (battery operated) and that has a fixed single output (+5V, +3.3V are the voltages I am considering for now). It is going to provide power to a temperature sensor for a monitoring application. A battery would actually suffice but I am just preparing for scenarios where the battery output would not be stable anymore.

The TPS71550 and TPS71533 particularly caught my attention because these are designed to support MSP430 families, one of the components used in the project. However, I would like to hear better suggestions from more experienced users in this forum.

Thanks,
Brennan

What's the difference between TPS73125DVBT and TPS73125DVBTG4?

Arrow Vancouver — Tue, 20 Oct 2009 02:17:25 GMT

Hi, what does the "G4" stand for in the part number? Thanks!

uA7805 Linear Regulator

John Beaty — Wed, 23 Sep 2009 19:59:00 GMT

Can anyone point me to an application circuit for adding a pass transistor (like a 2N3055) for added current availibility from a uA7805?

I am also interested in the math in calculation any needed for any additional components (like biasing resistirs).

The application is for about a continuous 2A @ 5V.

Thanks

John

TPS73201 Reverse Current Issue

Matty — Tue, 29 Sep 2009 20:44:41 GMT

Hi,

I am planning on using the TPS73201 in my design. Unfortunately, I don't have much control over how the system will power down (i.e if EN is driven low before Vin is removed) as recommended by the datasheet.

Does anyone know what will happen if EN is active after the input voltage is removed? Will there be any damage to the part?

Thanks!

TPS74201 Reverse Current Protection

Samuel Fritzinger — Mon, 28 Sep 2009 20:37:37 GMT

I am using the TPS74201 LDO. I plan to possibly crowbar the input voltage. I looked through the datasheet for any information regarding what the device can handle as far as reverse currents and duration, but couldn't find anything. I know there must be some limitation as to how much capacitance you can have on the output before the reverse current will effect the chip. I simulated the Pspice model from the TI website, with a protection diode from the output to the input. It showed that most of the crowbared current flowed through the device and not the protection diode. Do these series of LDOs have reverse current protection and to what limitations?

Negative Linear Regulator

gge — Thu, 24 Sep 2009 14:38:30 GMT

Hello

Thanks for any help in this area. I am looking for a negative linear regulator that can both source and sink mAs of current.

Thanks

Gary

TPS79850 FB Resistors

Cosmin P — Tue, 11 Aug 2009 22:10:02 GMT

What is the range for the R1+R2 feedback divider internal to the fixed output TPS79850?

Power supply design

HITESH VANJANI — Mon, 24 Aug 2009 20:52:06 GMT

Hello,

My name is Hitesh and I am trying to make a basic power supply that can deliver 300mA @ 5.10 volts DC. I am using a basic setup which includes transformer (this is been hand made by me), followed by a full wave rectifier, a smoothing filter and a linear regulator. Everything is working fine accept the Ground on the secondary side of the transformer.

I know the secondary of the transformer is never grounded (untill its center tap which is not in my case) and after the Full wave Rectification and smoothing the AC is converted to DC with some ripple on in which is then supplied to a linear regulator, till this point everything is fine no problems taking readings and stuff but once the linear regulator comes in to the picture some thing seems so get upset. I mean the regulator gets upset with its ground, As this power supply i am designing is ment for wireless power transfer I cannot use the same groung as I did for the primary side of the transformer, by the way it is an air core transfromer with 2:1 turn ration. I have tried so many different things to give a proper ground to the regulator but it seems like it is not working, I know this issue will get solved once everything is on PCB but before that I want to test it before putting ON to PCB. Can anyone advice me abt what I should use for the ground which will be separate than the earth, Scope, Function Generator ground.

Waiting for the replies

Hitesh

Capacitor Power Supply

kanaga raj — Mon, 17 Aug 2009 09:40:25 GMT

I'm using capacitor power supply to Msp430.In this power supply using three phase,two and single phase supply.In this three and two phase are properly working but in single phase was not properly working.

Input:

240V/50Hz

Output:

5v/30mA is required.

In this i'm now using 100ohm resistance,1.4uF capacitor and 5.6V zener diode with 3.3v regulator need 5v input supply.

Only getting upto voltage of 3.8v for input to regulator.

Wat can i do for getting 5V supply to the regulator.

I already refereed the document(SLAA024) for design process, from this i cant get the proper solution.

TPS74301 Simultaneous Sequencing

Sornam Viswanathan V — Thu, 23 Jul 2009 09:08:05 GMT

Hello,

I am using the TPS74301 LDO to generate a rail that is supposed to simultaneously track a reference voltage during startup. The datasheet says " By properly choosing values of resistor divider used to feed the track pin, one can implement Simultaneous and ratiometric startup". From my understanding of the device, It makes the output voltage track the track pin voltage if the voltage at the track pin is less than 0.8V, and after that the output voltage tracks the Set point.

If we use a voltage divider to generate the track voltage, doesn`t it become ratiometric sequencing by default ?The voltage at the track input (output of the voltage divider) will be a ratio of the input to the voltage divider. Kindly clarify. If that is the case, how does changing the value of the resistor divider enable ratiometric or simultaneous sequencing ?

Thanks in Advance!

Ps: the part i am refering to is the TPS74301, LDO with programmable sequencing .

Poor regulation on TPS76201

heyneman — Tue, 09 Jun 2009 18:57:44 GMT

I'm using a TPS76201 to set a reference voltage in my circuit. This voltage does need to sink/source current, but should be well below the 100mA limit. When my circuit is powered but inactive, the TPS76201 output is as expected, but after a short amount of activity the output voltage rises (from 3.5V -> 4.3V roughly). When I scope the FB pin (nominal 0.6663V internal reference) I find that it climbs as high as 0.9V, which would explain the increased output voltage.

Any thoughts? Could I be sourcing/sinking more current than I expect, and would that cause the output and FB pin voltages to change so drastically?

Thanks for any help.

-heyneman

Misleading Information about dual-voltage LDO (TSP780) in Datasheet

michi — Wed, 20 May 2009 23:34:41 GMT

If I am not totally confused right now then there an error in tables 4 and 6 of the datasheet. The results in those tables are skewed because they don't take into account the power that is dissipated by the voltage regulator, which is (V_in - V_out) * I_load. They only consider the contribution of (V_in * I_q).

While the TPS780 would still be better than the imaginary "typical" LDO the difference would be slightly less than advertised in this example.

LDO73133

Michelle — Wed, 22 Apr 2009 13:29:55 GMT

Does the TPS73133DBVT and the TPS73133MDBVREP packaged parts use the same die?

Current limitation techniques in CMOS LDO regulator?

Sebastien — Fri, 10 Apr 2009 14:25:18 GMT

Trying to find out information on how current limiting is implemented in CMOS LDO regulators but so far failling miserably.

Any information on the subject would be welcome.

Cheers,

Sebastien

TPS73201 enable pin slew rate

Scot Lester — Wed, 08 Apr 2009 14:02:18 GMT

Are there any limitiations on how slow the EN pin can come up on the TPS73201? For example a really slow RC pull up?

Fixed voltage regulator(are external L and C necessary for device to work)

Richard Do — Thu, 19 Mar 2009 18:58:31 GMT

Hi all, I just have a simple questions. I am using TPS62203, which is a fixed voltage regulator of 3.3V. In the datasheet, I am supposedly to use some external capacitors and an inductor with the chip. I was wondering if it is necessary to use them. Please let me know. Thanks!!!

TPS74801 - Thermal data does not agree with data in the QFN app note

Scot Lester — Thu, 08 Jan 2009 18:17:00 GMT

Question/Problem:

Thermal data does not agree with data in QFN app note

Answer:

The app note is for the RGY package and the TPS74401 uses the RGW package. They are slightly different in size and pin out. Also, the app note boards are JEDEC compliant.

TPS795xx - At what Vin-Vout does PSRR start falling?

Scot Lester — Thu, 08 Jan 2009 18:13:38 GMT

Question/Problem:

At what Vin-Vout does PSRR start falling?

Answer:

For a PMOS pass element based LDO, the PMOS FET provides some gain to the loop which is directly proportional to PSRR. As Vin approaches Vout, the pass element moves from the linear region into saturation so it can't provide gain anymore. For the TPS795, PSRR drops significantly for Vin-Vout < 0.4V. Later IC datasheets have curves with lower Vin-Vout.

TPS73701 - The data sheet does not contain a plot showing noise spectrum vs NR cap.

Scot Lester — Thu, 08 Jan 2009 18:10:18 GMT

Question/Problem:

The data sheet does not contain a plot showing noise spectrum vs NR cap.

Answer:

Refer to the TPS73601 which has the same core and curve.