DEV Community: ChipApex

Notes on the Infineon 111-3013: a 400 kHz buck/boost controller in 8-SOIC

ChipApex — Thu, 22 Oct 2026 04:03:49 +0000

The Infineon 111-3013 is a single-output DC-DC switching controller in an 8-SOIC. It drives an external power transistor and can run either buck or boost with a positive output. The notes below are the parameters I check before keeping a part like this on a repair BOM or a small new board.

What the listing actually specifies

Function is step-up and step-down. Topology is buck and boost, one output, one phase. Output type is a transistor driver. Synchronous rectification is supported. Clock sync is not. The control features called out are Enable and Soft Start. There is no serial interface.

Supply (VCC/VDD) is 4.2 V to 25 V. Switching frequency is 400 kHz. Maximum duty cycle is 90%. Operating temperature is 0 °C to 70 °C ambient, so this is a commercial-range part. Mounting is surface mount. The package is 8-SOIC, 0.154 in (3.90 mm) body width, supplier device package 8-SOIC, shipped in tube. The short description on the manufacturer line is IC REG CTRLR BUCK/BOOST 8SOIC.

The parameter table I used is the one on the Infineon 111-3013 buck/boost controller page. Treat that table as a starting point and confirm pinout, gate-drive voltage, and current limits in the datasheet before layout.

Design notes

400 kHz keeps the inductor and the output capacitors smaller than a 100 kHz design, but gate-drive loss on the external FET is not free. If the FET is picked for a very low Rds(on), its gate charge may be large. At 400 kHz that charge is switched every cycle. Check Qg against whatever drive the controller can actually source and sink. The short description does not state the drive current.

The 90% duty-cycle cap matters more in boost than in buck. A buck from 12 V to 5 V is nowhere near 90%. A boost from a sagging 4.2 V input toward a much higher rail can hit the limit, and Vout will then fall with Vin. Do the Vout/Vin math, including diode or sync-FET drops, before locking the topology.

Synchronous rectification is listed as yes. That usually means a second gate drive for a sync FET instead of a diode. Dead time and the high-side or low-side arrangement are not in the short spec. Scope the switch node on the first prototype and look for shoot-through before you trust an efficiency number from a spreadsheet.

Enable plus soft start is the useful pair for sequencing. Soft start limits inrush into a large output capacitor. There is no clock-sync input, so two of these controllers on one board will free-run. If you need to avoid a beat frequency between two nearby switchers, this is the wrong part.

The ambient rating stops at 70 °C. A sealed enclosure that runs hotter than that needs a wider-temperature controller, or a measurement of the real board temperature with a plan to derate. Catalog TA is not the temperature at the switch node.

Public records list 111-3013 as obsolete. An 8-SOIC footprint match is not a second-source plan. For a new design I would treat this as a legacy or repair item and pick a current buck or boost controller with a stated lifetime. For a board that already uses it, the 8-SOIC is straightforward to rework, but do not assume pinout from the function string. Buck and boost controllers in the same package do not share a pinout.

What I would check on the bench

Confirm VCC stays inside 4.2 V to 25 V through startup and through input steps, including a source that is still rising.
Measure the switch-node frequency. It should sit near 400 kHz. The short spec does not mention spread-spectrum or a burst mode.
At minimum input and maximum load, watch the duty cycle. If it sits on the 90% rail and the output sags, the conversion ratio is the problem, not only the feedback divider.
Capture the soft-start ramp into the real output capacitance, not into an electronic load set to a light constant current.
If a sync FET is fitted, look at both gate drives and the switch node together before you call the design quiet.

Series, grade, and qualification are blank on the listing. Do not read those blanks as "industrial" or "AEC-Q". They are unspecified.

Battery Management IC Notes

ChipApex — Fri, 16 Oct 2026 06:15:39 +0000

Battery management ICs handle cell balancing, protection, and gauging. Compare options at ChipApex electronic components.

Picking MOSFETs for Switching: Rds(on), Vgs and Gate Charge Explained

ChipApex — Fri, 16 Oct 2026 01:44:37 +0000

Choosing a MOSFET for a switching application, such as a buck converter, motor driver or load switch, is a trade-off between conduction loss, switching loss and drive requirements. Three datasheet parameters do most of the work: Rds(on), gate threshold and drive voltage (Vgs), and gate charge (Qg).

Rds(on) and conduction loss

Rds(on) is the drain-source resistance when the device is fully enhanced. Conduction loss is simply I² x Rds(on). Remember that Rds(on) rises with junction temperature, often by 50-100% at 125 C, so use the hot value from the datasheet curves rather than the headline 25 C number. A lower Rds(on) usually means a larger die, which brings higher capacitance and gate charge.

Vgs: threshold versus drive voltage

The threshold voltage Vgs(th) is where the device just begins to conduct, typically at a tiny drain current such as 250 uA. It is not the voltage at which the part is fully on. Look at the Rds(on) rating conditions: a part specified at 10 V needs a 10 V driver, while logic-level MOSFETs are specified at 4.5 V or even 2.5 V for direct microcontroller drive. Also respect the maximum Vgs, commonly plus or minus 20 V, and watch for ringing that can exceed it.

Gate charge and switching loss

Qg tells you how much charge the driver must supply to switch the device. Drive power is roughly Qg x Vgs x fsw, and switching speed depends on the driver's peak current: transition time is about Qg divided by gate current. At high frequency, the figure of merit Rds(on) x Qg is a useful way to compare devices. For a high-side or high-frequency design, prioritize low Qg and Qgd (the Miller charge); for a low-frequency, high-current design, prioritize low Rds(on).

Other considerations

Vds rating: leave 20-30% margin above the maximum bus voltage, plus any inductive spikes.
Body diode: reverse recovery charge matters in half-bridge circuits.
Package and thermal path: a tiny Rds(on) is useless if the package cannot shed the heat. Check RthJA and the copper area on your PCB.
SOA: linear-mode operation, such as hot-swap, needs a safe operating area check.

Putting it together

Start with voltage and current, pick a drive level your controller can provide, estimate conduction and switching losses at your frequency, then verify with thermal calculations. When you are ready to shortlist candidates, you can browse a range of MOSFETs and compare Vds, Rds(on) and package side by side. Always confirm the final choice against the datasheet and measure switching waveforms on the bench.

TVS Diodes for ESD and Surge Protection: The Basics

ChipApex — Fri, 16 Oct 2026 01:35:32 +0000

Every connector on your board is an antenna for trouble. A user touching a USB port can inject kilovolts of electrostatic discharge (ESD), and long cables or inductive loads can add surges that last microseconds to milliseconds. A transient voltage suppressor (TVS) diode is the simplest way to keep those events away from your IC pins.

How a TVS diode works

A TVS is a silicon junction that sits in parallel with the line you protect. Under normal operation it is high impedance. When voltage exceeds its breakdown level, it avalanches and clamps the line, shunting the energy to ground. When the event ends, it recovers on its own, with no fuse to replace.

Key parameters

Standoff voltage (VRWM): the maximum working voltage with negligible leakage. Choose it at or above your signal or rail voltage.
Breakdown voltage (VBR): where conduction begins, typically 5-10% above standoff.
Clamping voltage (VC): the voltage seen by your circuit at a specified peak pulse current. This must stay below the absolute maximum rating of the protected device.
Peak pulse power or current (IPP): surge capability, usually rated on an 8/20 us waveform. ESD ratings follow IEC 61000-4-2 (contact and air discharge).
Capacitance: critical for high-speed lines. USB 3, HDMI and Ethernet need low-capacitance arrays, often below 1 pF, while power rails can use large, rugged parts.
Unidirectional vs bidirectional: use unidirectional for DC rails and single-ended signals, bidirectional for AC or signals that swing negative.

Layout matters as much as the part

Place the TVS as close to the connector as possible, before any series components. Route the signal through the TVS pads rather than stubbing off it, and use a short, wide, low-inductance path to a solid ground. Even a few millimeters of trace adds inductance that produces a voltage spike during a fast ESD edge, defeating a perfectly good diode.

Choosing a part

Start from the interface: find the maximum signal voltage, the data rate (which limits capacitance), and the required standard level, such as 8 kV contact ESD or a surge rating for industrial ports. Then verify the clamping voltage against the protected IC's limits. If you are sourcing parts, a reliable TVS diode supplier will list these parameters clearly so you can filter by standoff voltage, package and capacitance: TVS diode supplier.

Summary

Pick standoff voltage just above your operating voltage, check that the clamp voltage is safe for the downstream IC, match capacitance to your data rate, and place the device right at the connector. Then test with an ESD gun if you can.

How to Choose Aluminum Electrolytic Capacitors: Ripple Current, ESR and Lifetime

ChipApex — Fri, 16 Oct 2026 01:34:30 +0000

Aluminum electrolytic capacitors are the workhorse of bulk energy storage and filtering in power supplies, motor drives and LED drivers. They offer high capacitance per dollar, but they are also the most common wear-out part on a board. Picking the right one comes down to three numbers: ripple current, ESR and rated lifetime.

Ripple current

Every cycle of charge and discharge pushes current through the capacitor's internal resistance and heats it. The datasheet gives a maximum ripple current at a stated frequency (often 120 Hz or 100 kHz) and temperature. Switching converters usually produce ripple at tens or hundreds of kHz, so use the datasheet's frequency multiplier table. Calculate the RMS ripple current in your circuit and keep at least 20-30% margin below the rated value.

ESR

Equivalent series resistance sets both heating (I² x ESR) and output ripple voltage. Low-ESR and polymer-hybrid series are designed for switching supplies, and ESR also rises sharply at low temperature, which matters for outdoor equipment. If your output ripple is too high, paralleling two smaller parts is often better than one large one because ESR and ripple rating both improve.

Lifetime

Lifetime is quoted as hours at maximum temperature, for example 2000 h at 105 C. A common rule is that life doubles for every 10 C drop in core temperature. A 2000 h part running at 65 C core temperature could last 2000 x 2^4 = 32,000 hours, roughly 3.6 years of continuous operation. For a ten-year design life, pick a 5000 h or higher series or reduce thermal stress by placing the part away from heat sources.

Other selection tips

Derate voltage: use a rated voltage at least 20% above the worst-case bus voltage, more for surge-prone lines.
Check case size and lead spacing against your layout and vibration needs.
Look at leakage current if the circuit is a low-power or timing application.
Avoid placing the capacitor next to hot inductors or heatsinks.

When you are ready to compare series and ratings, browse a catalog of aluminum electrolytic capacitors and filter by voltage, capacitance, temperature rating and lifetime. Always confirm final values against the manufacturer's datasheet and validate temperature rise on a real prototype.

Summary

Match ripple current at your actual switching frequency, minimize ESR where heating and ripple matter, and use the lifetime formula to verify the part will survive your product's service life. A little margin here prevents the field failures that electrolytics are known for.

How to Verify Genuine IC Chips Before Bulk Ordering

ChipApex — Fri, 16 Oct 2026 01:25:45 +0000

Counterfeit and remarked ICs are a real risk when you buy in volume. A bad batch can cost far more than the savings, so it pays to run a simple verification routine before committing to a bulk order.

1. Vet the supplier

Ask for the company registration, a clear return policy, and traceability documents. Reputable sources such as authorized distributors or established suppliers like ChipApex electronic components should be able to provide batch and date codes on request.

2. Inspect the markings

Compare the logo, font and laser etching against the manufacturer datasheet.
Check that date codes are plausible for the part's production period.
Look for sanded tops, uneven surfaces or residue, which suggest remarking.

3. Order samples first

Buy a small quantity and test it on a real board. Check key parameters such as supply current, voltage thresholds and timing against the datasheet, not only whether it powers on.

4. Verify the packaging

Genuine reels and trays have consistent labels, moisture barrier bags with humidity cards, and intact seals. Mismatched barcodes or a poor print quality are warning signs.

5. Use basic lab checks

If budget allows, do X-ray or decapsulation checks on a sample, or at least a microscope inspection. For IoT products, also compare the electrical signature of sample units against a known-good part.

6. Document everything

Keep photos, lot numbers and test results for each shipment. If a problem appears later, this record makes returns and root-cause analysis much easier.

Takeaway

Verification does not have to be expensive. Combine supplier checks, sample testing and careful incoming inspection, and you will catch most problems before they reach your production line.

DEV Community: ChipApex

Notes on the Infineon 111-3013: a 400 kHz buck/boost controller in 8-SOIC

What the listing actually specifies

Design notes

What I would check on the bench

Further reading

Battery Management IC Notes

Picking MOSFETs for Switching: Rds(on), Vgs and Gate Charge Explained

Rds(on) and conduction loss

Vgs: threshold versus drive voltage

Gate charge and switching loss

Other considerations

Putting it together

TVS Diodes for ESD and Surge Protection: The Basics

How a TVS diode works

Key parameters

Layout matters as much as the part

Choosing a part

Summary

How to Choose Aluminum Electrolytic Capacitors: Ripple Current, ESR and Lifetime

Ripple current

ESR

Lifetime

Other selection tips

Summary

How to Verify Genuine IC Chips Before Bulk Ordering

1. Vet the supplier

2. Inspect the markings

3. Order samples first

4. Verify the packaging

5. Use basic lab checks

6. Document everything

Takeaway