Power management forum - Recent Threads

BQ25306: POL floating

FRANK1 — Fri, 09 Oct 2026 21:30:04 GMT

Part Number: BQ25306

Hi Team,

We have planning to use your stan-alone charger control chip, the BQ25306, in or design. We bought the BQ25306EVM, and on POL pin for Stand-Alone Mode, is written should be left floating, but when this Pin Header JP2 is touched with hand or scope probe, then device stops to enter on charge mode, with EN = 0, and input DC 12V is represented. Most probably floating POL pin is influenced from external capacitance. I have tried to attach single cap = 10nF to POL pin. Then it behave more stable. In addition have atached also series 1K to 1nF Cap. What is your suggestion regarding this issue? Is there any solution for this issue?

Thanks in advance.

Regards,

Best Regards,
Frank Sun
Texas Instruments Customer Support Center

RE: BQ25306: POL floating

Sam Berendsen — Sat, 17 Oct 2026 14:13:22 GMT

Hi Taner,

If you choose to ground the POL pin, you will need a voltage divider to drive the EN pin when VBUS is applied. When designing this divider, ensure the voltage at the EN pin stays between 1.3V and 5V (to provide a safety margin). Note that for REGN to turn on, the chip must be enabled via the EN pin and VBUS must be greater than both the UVLO threshold and VBAT + 157mV (typical).

The RC filter provides some noise immunity on the POL pin. For additional stability, you can add a weak pull-up (e.g., 100kΩ–470kΩ) from the POL pin to REGN. This works in parallel with the internal POL bias, so a higher resistance is preferred to avoid loading the internal circuit.

As a design best practice, ensure your PCB layout minimizes the risk of capacitive coupling or accidental contact between the POL pin and ground. The POL pin is provided on the EVM for testing purposes and is typically not required in a final design.

Best,
Sam

BQ24650: Internal precharge timer issues

Eric Michat — Sat, 17 Oct 2026 12:53:21 GMT

Part Number: BQ24650

Hello there,

Sorry, but I think there is a big mistake in the chip design regarding the 30mn internal precharge timer when the battery is close to deep discharge state.

I explain the problem : a 12V battery is close to deeep discharge, let's say 10V. So the input feedback voltage at VFB is bellow 1.55 (V_LowV parameter in the data sheet).

We are at sunrise ; the solar pannel starts to produce a weak voltage, and above 12V, that wakes up the internal logic of the device (burst switching occurs). The internal timer starts, in order to limit the charging current to 1/10 th of the maximum current, to recover from a deeep discharge. The solar pannel continues to increase its power but not enought to rise the Vbat above the 1.55V threshold within 30mn. The charger goes to fault mode and remains in this state "for ever" (at least untill a cut-off of the input power or a restart of the charging sequence by pulling MMPSET to GND. Even if the solar power goes to its maximum during the same day, the charger will never resume from itself.

This problem does not appear whem the charger starts with a VFB above 1.55V, fortunately.

So in this situation, the only workarround should be to add an external circuitry that applies a reset pulse to the MMPPT pin when Vin rises above a certain level. It cannot be done by my uC because in deep discharge condition, by definition, the electronic of the board is switched off and placed in low power standby mode.

Am I missing something here (I would prefer to !) or am I right ?

It's a pitty, because the chip works fine in terms of power, even with larger MOSFET and the two regulation loops VFB and MPPSET are very stable.

Thank you for your reply.

LM4050-N-Q1: Driving Low Load Current

Nishant Gupta — Wed, 14 Oct 2026 20:08:34 GMT

Part Number: LM4050-N-Q1

Hello TI Team,

I would like your guidance on whether this IC is suitable for converting 24 V DC to 5 V DC for my application.

Input voltage: 24 V DC from a DC-DC converter
Output voltage: 5 V DC
Normal load current: 40–50 mA
Maximum anticipated load current: 350 mA

My questions are:

Can this IC reliably support the above load current, including the maximum 350 mA?
If a Zener diode is used, will it provide the required voltage regulation immediately when 24 V is applied, or does it require a minimum breakdown current?
How can I ensure that the 5 V supply starts reliably whenever the 24 V input is switched on?
Is there a suitable space-grade or space-qualified TI device for this application? If the proposed approach is unsuitable, please recommend a reliable alternative.

My priority is reliable startup, stable 5 V output, sufficient current margin, and suitability for space applications.

Thank you for your support.

Best regards

RE: LM4050-N-Q1: Driving Low Load Current

Nishant Gupta — Sat, 17 Oct 2026 12:39:52 GMT

Hi Elizabeth Won,

Could you please assist me in procuring 2–3 samples of the LM4060A50EDBZRQ1 for initial testing and performance evaluation?

Your support in arranging these samples would be greatly appreciated.

Thank you for your assistance.

Best regards,
Nishant

RE: TLV776: Start-up Behavior

Stephen Ziel — Sat, 17 Oct 2026 10:44:07 GMT

Hey Cameron,

It's microseconds. The plot annotation is incorrect. I've added this to our datasheet correction log to be fixed in the next iteration of the datasheet.

Thanks,

Stephen

TLV776: Start-up Behavior

Cameron Perl — Fri, 16 Oct 2026 19:38:43 GMT

Part Number: TLV776

Hey team,

It was noted that in section 5.6 we call out t_STR as 320us but then figure 5-13 is showing its rise time in ms. Which one is correct?

Thanks,

Cam

LM5148: OUTPUT VOLTAGE ISSUE

Prabhat kumar — Sat, 17 Oct 2026 09:53:17 GMT

Part Number: LM5148

PDB_TEST MODULE.pdf

UCC2897A: UCC2897A – Output Voltage Oscillation at Light Load Below 550mA in PMP8861-Based Isolated DC-DC Converter

Udhayakumar T — Sat, 17 Oct 2026 06:31:25 GMT

Part Number: UCC2897A

Hello TI Support Team,

I am designing an isolated DC-DC converter using the UCC2897A controller, based on the PMP8861 reference design. The converter operates correctly over the full input voltage range at medium and full load. However, I am experiencing output voltage oscillation under light-load conditions.

1. Converter Specifications

Converter topology: Isolated DC-DC converter
Controller: UCC2897A
Reference design: PMP8861
Input voltage range: 18V to 80V
Output voltage: 24V
Output current: 4A maximum
Switching frequency: 200kHz
Output inductor: 27µH
Transformer magnetizing inductance: 67µH
Transformer leakage inductance: 90nH
Secondary-side rectification: Diode rectification

2. Observed Issue

The converter operates correctly across the entire input voltage range from 18V to 80V at an output load current of 550mA to 4A.

However, when the output load current drops below 550mA, the output voltage starts oscillating.

3. Support Required

Could you please help me identify the possible cause of this light-load output voltage oscillation?

Could this issue be related to the UCC2897A feedback loop compensation or control-loop stability at light load?
Could the controller's pulse-skipping or operating mode at light load contribute to this behavior?
What modifications would you recommend to eliminate the oscillation and achieve stable output regulation across the entire load range, including below 550mA?

Any suggestions regarding compensation component selection, feedback-loop tuning, or recommended design modifications would be greatly appreciated.

LM51770-Q1: The LM51770 tends to oscillate when it's in the transition area between BUCK and BOOST.

Peichuan Lu — Sat, 17 Oct 2026 06:14:56 GMT

Part Number: LM51770-Q1

The LM51770 connects a supercapacitor to VIN as a backup power source. When the VOUT bus voltage is 24V and the supercapacitor charges to around 20V (in the transition region between BUCK and BOOST), the output voltage ripple increases and it also makes a noise.

The loop parameters are calculated using the Excel calculator.

LM51770.rar

RE: LM5146: Interleaved Buck with CC/CV regulation

DKelektronik — Sat, 17 Oct 2026 05:28:04 GMT

Thank you for your response, and sorry for the delayed reply as I needed some time to verify the provided details.

Regarding your recommendations, I have a few follow-up questions:

VCM vs. PCM Implementation: With " Refer these for CV-CC implementation:...." . The two documents/references you provided for CV-CC regulation seem to be tailored for Peak Current Mode (PCM) controllers. Since the LM5146 uses Voltage Mode Control (VCM), are these two methods still fully applicable to the LM5146?
CC/CV with Interleaved Operation: The test report you shared (LM5146-Test-Result.pdf using the breakout board with LM5146EVM) aligns very well with our project requirements. However, can this CC/CV implementation be combined with interleaved operation?
Current Feedback Sharing in Interleaved Setup: If interleaved operation with CC/CV is feasible, how should the CC loop feedback be configured? For a total CC limit of 13A, should the current feedback be set to regulate 6.5A per channel, or does the CC loop adjust the overall current feedback differently?

Thank you again for your valuable support. I look forward to your guidance!

LM5146: Interleaved Buck with CC/CV regulation

DKelektronik — Thu, 08 Oct 2026 09:35:23 GMT

Part Number: LM5146

Hi TI Team,

We are designing a DC-DC converter with the following specifications:

Input Voltage: 35V – 65V
Output: 14.5V / 13A
Control Requirements: Constant Current / Constant Voltage (CC/CV) regulation

To handle this power level, we plan to implement a 2-phase buck converter architecture using two LM5146 controllers. According to TI app note SSZT900, the LM5146 supports multiphase/interleaved operation. However, we could not find explicit documentation on implementing CC/CV regulation in this configuration.

Could you please clarify the following:

Is the LM5146 capable of supporting both interleaved operation and CC/CV regulation simultaneously?
If yes, do you have any reference designs or recommended circuit configurations/application notes for implementing CC/CV control with the LM5146 in an interleaved setup?

Thanks and best regards,
Ngoc Hoan

UCC14240-Q1: UCC14240-Q1: Output Voltage Regulation Below 18 VHello TI Team, I am evaluating the UCC14240-Q1. The datasheet specifies an adjustable (VDD − VEE) output voltage range of 18 V to 25 V. My application requires a regulated 13 V output across V

Vikas Kumar — Sat, 17 Oct 2026 05:01:38 GMT

Part Number: UCC14240-Q1

Hello TI Team,

I am evaluating the UCC14240-Q1. The datasheet specifies an adjustable (VDD − VEE) output voltage range of 18 V to 25 V.

My application requires a regulated 13 V output across VDD and VEE.

Requirement:
• Input voltage: 24 V (nominal)
• Output voltage: 13 V
• Output power: 1.5 W to 2 W

Could you please confirm whether 13 V output regulation is supported?

If not, could you please suggest an alternative TI isolated DC/DC solution that can provide a regulated 13 V output with the above requirements.
Additionally, could you please provide a TINA-TI simulation model (if available) for the UCC14240-Q1 device?

Thank you

Best regards,

Vikas Kumar

RE: UCC21551CQEVM-079: Maximum Load Current Supported by UCC21551CQEVM-079 EVM PCB

Vikas Kumar — Sat, 17 Oct 2026 04:41:43 GMT

Thank you, Will

UCC21551CQEVM-079: Maximum Load Current Supported by UCC21551CQEVM-079 EVM PCB

Vikas Kumar — Wed, 14 Oct 2026 10:02:52 GMT

Part Number: UCC21551CQEVM-079

Hi TI,

I am planning to use the UCC21551CQEVM-079 for isolated converter application.

I would like to know the maximum practical load current that can be supported when using the onboard MOSFET locations on the EVM PCB.

My operating conditions are:
• DC bus voltage: 9 V
• Output power: 500 W
• Load current: ~56 A
• Switching frequency: 100kHz

Can the EVM PCB traces, connectors, and MOSFET mounting arrangement safely support this current level, or is TI's recommendation to use the EVM only as a gate-driver evaluation platform and implement the power MOSFETs on a separate power PCB ?
Can this EVM PCB used for high power and low voltage application ?

Any guidance on the PCB current capability or thermal limitations of the EVM would be appreciated.

UCC27302A: UCC27302A for 3-phase motor-driver application

Narek Pezeshkian — Sat, 17 Oct 2026 01:25:13 GMT

Part Number: UCC27302A

Hello,

I would like to use three UCC27302As, each driving one phase of a brushless motor. The operating frequency would be somewhere in the range of 12kHz - 96 kHz. Max bus voltage is 40V. Are there any reasons the UCC27302A would be unsuitable for such an application?

Thanks,

Narek

LMZM33606: LMZM33606 negative output

Joe Miller1 — Wed, 14 Oct 2026 00:08:55 GMT

Part Number: LMZM33606

Hi,
I want to use the LMZM33606 with a 12V input to produce a -5V output.
I have some questions relating to some of the pins.

BIAS_SEL pin of LMZM33606 should be connected to PGND pin of LMZM33606 (-5V)

SYNC/MODE pin of LMZM33606 should be connected to VCC pin of pin of LMZM33606 for FPWM mode.

Is it possible to get a schematic check offline?

Thank Joe

RE: LMZM33606: LMZM33606 negative output

Joe Miller1 — Sat, 17 Oct 2026 01:13:50 GMT

Hi,

Internal bias. FPWM mode.

Thanks Joe

RE: TPS92620-Q1: PWM Frequency

Jaya Bharath Reddy Kamatam — Sat, 17 Oct 2026 00:12:19 GMT

Hi Alex,

Thanks for your response.

At the moment, I do not have the required application information readily available. I will review it and get back to you.

In the meantime, could you please help verify the maximum allowable PWM frequency based on the timing parameters specified in the datasheet?

My current assumption is that the minimum PWM period should account for the relevant delays and transition times:

PWM ON delay = 3.7 µs
Rise time = 4.0 µs
PWM OFF delay = 1.8 µs
Fall time = 5.7 µs

Therefore:

Tmin = tON_delay + tr + tOFF_delay + tf
     = 3.7 + 4.0 + 1.8 + 5.7
     = 15.2 µs

Fmax = 1 / Tmin
     ≈ 65.8 kHz

Based on this calculation, I estimate the maximum PWM frequency to be approximately 65 kHz.

Could you please let me know whether this calculation method and result are correct, or if there is a more appropriate way to determine the maximum PWM frequency for this device?

Thanks & Regards,
Jaya Bharath Reddy

TPS92620-Q1: PWM Frequency

Jaya Bharath Reddy Kamatam — Fri, 16 Oct 2026 13:06:08 GMT

Part Number: TPS92620-Q1

Hello Team,

I have a general question regarding the TPS92620-Q1 LED driver that we are using in our application.

The datasheet recommends a minimum PWM frequency of 200 Hz for brightness control. My question is: what is the maximum PWM frequency that can be used while still satisfying the LED on-time and off-time requirements?

Thank you for your support.

UCC12041-Q1: UCC12041-Q1: Excessive 8 MHz conducted EMI coupling into PCB ground planes

Glen Kleidon — Sat, 17 Oct 2026 00:04:30 GMT

Part Number: UCC12041-Q1

We are seeking TI's technical assistance with an 8 MHz conducted-emissions compliance failure associated with the UCC12041-Q1 isolated DC/DC converter in our DCMax solar PV controller.

Background

Our original PCB design exhibited RF emissions that necessitated a substantial PCB redesign. The revised 4 layer PCB successfully addressed those RF emissions, incorporating improved filtering, grounding and layout arrangements consistent with TI's design recommendations.

However, despite resolving the original RF emissions problem, the revised design continues to exhibit a significant conducted-emissions disturbance at approximately 8 MHz, corresponding to the UCC12041-Q1's internal switching frequency.

Independent EMC testing to AS/NZS 61000.6.3:2021 identified this disturbance as the remaining issue preventing compliance. The measured emissions exceed the applicable 60 dBµV average limit at 8 MHz.

PCB design and filtering

The revised PCB incorporates:

Inter-domain capacitive coupling between isolated ground regions, following TI's recommended approach.
Local supply decoupling.
Multiple filtered PCB ground and supply regions.
Common-mode chokes and ferrite beads on both 5 V and GND connections between regions.

The original and revised PCB designs have approximately 71 pF and 141 pF of measured inter-domain capacitance respectively. The revised design demonstrated approximately 4 dB improvement in the 8 MHz disturbance, although several layout and filtering changes were introduced simultaneously. These included separating the island domains by a larger distance and increasing the internal capacitance plate overlay on L2 and L3

Investigation findings

We have conducted extensive diagnostic testing using a spectrum analyser to compare relative 8 MHz signal levels.

The disturbance can be detected on virtually every cable leaving the sensor board, In particular the DC connections requiring compliance conductance testing which are the ground reference for the isolated side. It propogates over the Cat 5 cabling to the controller onto power connections, ground conductors and the LCD cable but these are not significant for the compliance testing.

We have also investigated the effects of inter-domain capacitance. Adding external capacitance between the isolated domains generally increased the 8 MHz disturbance rather than reducing it. Removing substantial portions of the original PCB's intentional capacitive copper structures did not materially improve the result.

Additional filtering of the external sensor cables has also provided little improvement.

These observations suggest that the converter's 8 MHz switching activity is coupling into the PCB and external wiring, but we have not conclusively identified whether the dominant mechanism is conducted common-mode current, capacitive coupling, magnetic coupling or a combination.

Assistance requested

We would appreciate TI's engineering guidance on the following:

What are the principal common-mode emissions mechanisms associated with the UCC12041-Q1's internal 8 MHz switching operation?
Given that the revised PCB follows TI's recommended design practices and has resolved the original RF emissions problem, what additional measures would TI recommend specifically for reducing conducted emissions at 8 MHz?
How should the inter-domain capacitance be optimised for conducted emissions, particularly when increasing capacitance appears to worsen our measurements?
Can the converter's switching fields couple directly into surrounding PCB copper independently of noise conducted through its power connections?
Does TI have reference designs, application notes or test results addressing conducted-emissions performance of the UCC12041-Q1 in systems with external cabling?

We can provide our schematic, PCB layouts, independent EMC test results and details of the diagnostic experiments.

Assembly 2.pdf

LMR51450: Thermal management and PCB layout advice

Phil Rittenhouse — Sat, 19 Sep 2026 22:49:36 GMT

Part Number: LMR51450

Hi,

I have built a small DC-DC converter around the LMR51450 with the goal of outputing up to 5A at 5V. Unfortunately the chip is running hotter than I would like (110C at 3.1A) (see attached thermal image). Since it is hitting 110C on the case at only 3.1A, it seems unlikely it will handle 5A for any length of time.

I am using 2oz copper for the PCB. I have attached my schematic and top and bottom layers for review. Can you suggest any improvements I could make to improve the thermal performance? Is my goal of 5A reasonable?

Best regards,
Phil

5V_demo-B_Cu.pdf 5V_demo-F_Cu.pdf 5V_demo-Power.pdf

RE: LMR51450: Thermal management and PCB layout advice

Phil Rittenhouse — Fri, 16 Oct 2026 23:51:57 GMT

The new boards layout looks like it should do the trick. Thanks for your help

RE: LM5148: LM5148 Dual-Phase Buck Converter Current-Sharing Issue

Hakob Sargsyan — Fri, 16 Oct 2026 23:39:23 GMT

Hello Tim,

Thank you for your feedback and suggestions.

As a follow-up, I tested the current-sense filter with 49.9Ω and 1nF, reducing the RC time constant by a factor of 10 compared to the 10nF configuration. However, the current imbalance remained unchanged, with the same current distribution between the two phases.

I then replaced both LM5148 controller ICs with new samples and repeated the tests. The current-sharing issue was resolved, with the current imbalance typically around 5% and less than 10% in the worst case.

To further investigate, I also tested each of the two original ICs individually, pairing it with a new IC. One of the original ICs operated correctly, while the other reproduced the same current-sharing issue.

These results suggest that something may have gone wrong during our testing with the original ICs.

Thank you for your support and guidance.

Best regards,
Hakob

LM5148: LM5148 Dual-Phase Buck Converter Current-Sharing Issue

OhmMyGod — Sun, 11 Oct 2026 20:19:27 GMT

Part Number: LM5148

Hello TI Support,

We are having an issue with current sharing in our LM5148 dual-phase buck converter design. The primary phase carries significantly more current than the secondary phase and heats up considerably more.

I took the following measurements:

Total Output Current	Phase1	Phase2
15A	12.5A	2.5A
20A	15A	5A
25A	17.7A	7.3A

I found a recommendation on the TI E2E forum to change the current-sense filter resistor to 49.9Ohm and the capacitor to 10nF. I tried these values, but the current imbalance remained unchanged.

I have attached the schematic and oscilloscope waveforms of the SW nodes for both phases for your review. Could you help us identify the possible cause and suggest further debugging steps?

Thank you