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TLC555CDR Supply: Fab Expansion, Timer Fit and Ordering Decisions

For an engineering buyer, the useful response is to separate the planning horizons. A factory investment can inform a conversation about the manufacturer's future footprint. The next board build requires evidence about a particular package, quantity, shipment window and approved source. To connect those two decisions, ask which product information has actually changed.

Keep a proven TLC555CDR design on its approved BOM while reviewing concrete supply evidence. A news-driven substitution creates a new engineering task before it has established a purchasing benefit. Conversely, ignoring all manufacturing changes leaves the team poorly prepared when an affected-product notice or real delivery problem arrives. Use the time before an urgent buy to evaluate a credible fallback while normal purchasing continues.

Table 1 separates the evidence needed for each decision. It is an editorial framework for the buyer, not a description of TI's internal manufacturing sequence.

Table 1. Connect each supply question to evidence at the same level.

Source: TI's public manufacturing and product-change information; decision framework by YG GROUP.

The gap between stages is where purchasing assumptions usually enter. A quote might identify only “TLC555,” while the approved BOM specifies a carrier and temperature grade. A broad availability message might cover a package that the assembler cannot load. Closing those gaps early makes the factory news useful without demanding that it answer questions it never addressed.

Start with the orderable device you already approved

The final letter can change the purchasing conversation

TLC555CDR is an eight-pin SOIC device in TI's D package, with a commercial operating-temperature range of 0°C to 70°C. The supplied Rev. K datasheet's September 18, 2026 package addendum lists a standard quantity of 2,500 in large tape and reel. It marks TLC555CDR Active while marking the tube-format TLC555CD Obsolete. The exact TI ordering page, checked on September 23, 2026, shows the same status distinction.

That is a more actionable finding than a general statement about the timer family. A historical BOM that names the tube version needs a different purchasing review from one already specifying the reel. The logic function may be familiar to the design team, but the assembler still needs the correct feeder format, orientation and receiving record.

The status distinction also gives the headline a practical limit: even within one established device family, orderable options can have different lifecycle records. Broad manufacturing investment cannot be substituted for that record. Equally, an Active label does not reserve stock or fix a lead time. Record the status as a dated observation and obtain the commercial commitment separately.

Preserve the full TLC555CDR identity through the quote, order and receiving record. A shorthand family name is convenient in conversation; it is weak identification for a shipment that must match an approved assembly process.

Table 2. What the TLC555CDR identity means for this BOM.

Source: TLC555 datasheet, Rev. K, recommended conditions and package addendum; TI exact ordering page. Status checked September 23, 2026.

Match the grade to the real environment

The shared datasheet covers C, I, Q and M versions. Their common description makes it easy to carry a family-wide statement into the wrong BOM line. For this C-grade device, the recommended supply range is 2V to 15V and the specified free-air temperature range is 0°C to 70°C. Another member's temperature range or qualification does not extend those limits.

A proposed wider-temperature option deserves an engineering review rather than automatic rejection or acceptance. For example, Rev. K gives different recommended minimum supplies for different temperature grades. A design that works near the C version's lower supply boundary cannot assume that a broader-temperature part preserves the same low-voltage operating conditions. The designer should review the entire condition set, including startup, before approving the change.

Package names deserve similar care. The family includes packages with different pin counts. Matching the family title and overlooking the actual drawing can turn a seemingly routine sourcing decision into a board revision. Table 2 is deliberately anchored to the released code, so that purchasing and engineering are discussing the same physical device.

Know which timer behavior your product is buying

TLC555's appeal comes from a useful combination: an external RC network defines timing, CMOS inputs permit relatively small timing capacitors, and the output can interface with common logic under the specified conditions. These features can keep a modest timing task independent of firmware. Their value depends on the circuit around the chip.

Low power and output drive are different requirements

At 5V and 25°C, the Rev. K electrical table lists 180µA typical supply current under its stated operating configuration. That is a defined condition, not a promise for every switching frequency, output load or temperature. If the product's power budget depends on the timer, include the output load and switching behavior in the budget instead of multiplying a generic catalog figure by supply voltage.

The output is also asymmetric. At 5V, the datasheet specifies high-level output voltage under a −1mA load and low-level voltage at several sinking currents. The first-page headline of 100mA typical sink capability should not be read as 100mA source capability. Nor should it replace the electrical-table conditions used to determine a valid logic level.

Suppose the timer drives a logic input in the current product, but a suggested replacement will directly drive a heavier indicator load. That change affects more than the bill of materials. It changes output voltage, dissipation and potentially supply disturbance. A useful replacement review starts with the connected load, not a ranking of the largest current number on each product page.

A familiar pulse still needs a defined startup

The TLC555 inputs are level sensitive. In the monostable description, the trigger must return high before the timing interval ends; holding it low changes the expected behavior. RESET overrides the other inputs and must have a defined state. TI recommends a suitable pullup when external logic uses RESET, or a direct connection to the supply when reset functionality is unused.

That detail belongs in a supply review because a replacement often gets tested only after the board is already running. A timer that produces the expected frequency in steady state has not yet demonstrated the required first pulse, reset release or recovery after a supply interruption. Ask the engineer which of those events the equipment actually relies on.

Table 3. Translate timer features into conditions that protect the application.

Source: TI TLC555 Rev. K, sections 5.6, 6.3, 6.4 and 7.4; application interpretation by YG GROUP.

The layout guidance is concrete. TI recommends local supply bypassing using 0.1µF ceramic in parallel with 1µF electrolytic, placed close to the device, and a timing capacitor close to DISCH. It also shows a control-voltage bypass capacitor. These are useful starting points for the actual board review; they should not disappear because a replacement is described as lower power.

For exposed connections, component ESD ratings and system protection remain separate tasks. The datasheet includes an example protection network and sample board results. Those results are tied to the populated circuit and test conditions. They do not certify an untested product or make a sourcing change electrically invisible.

Put a number on the timing margin

A supply conversation improves when the engineer can say what may change and by how much. “The timer must be the same” can be unnecessarily restrictive; “any 555 will work” leaves too much undefined. A timing budget supplies a middle ground with an observable acceptance criterion.

A small astable example

Consider an illustrative 5V astable circuit using RA = 10kΩ, RB = 68kΩ and C = 10nF. These values are a worked example, not a tested YG GROUP board. For low-frequency operation, the datasheet gives:

• High interval: tH = 0.693 × (RA + RB) × C.
• Low interval: tL = 0.693 × RB × C.
• Period: T = 0.693 × (RA + 2RB) × C.
• Frequency for this calculation: f = 1 / T.

The nominal high interval is about 540.5µs and the low interval about 471.2µs. Together they give a period of approximately 1.0118ms, a frequency of 988.4Hz and an output-high duty cycle of 53.4%. This example uses the reciprocal of the calculated period consistently; small differences from a rounded 1.44 frequency coefficient are just rounding differences.

At roughly 1kHz, the example sits well below the datasheet's 100kHz boundary for discussing the simple equations. At higher frequencies, propagation delay, discharge resistance and parasitic capacitance increasingly matter. A catalog's maximum-frequency headline should therefore not be used as evidence that a particular RC design will retain its nominal accuracy near that headline.

Separate passive tolerance from the timer's own error

Assume, solely for this illustration, that both resistors have ±1% tolerance and the timing capacitor has ±5% tolerance. If both resistance contributions move to the same extreme, their weighted sum also changes by ±1%. Multiplying the extremes gives a period factor from 0.99 × 0.95 = 0.9405 to 1.01 × 1.05 = 1.0605. The corresponding calculated frequency spans roughly 932Hz to 1,051Hz.

That calculated range covers passive tolerances only; it is not a TLC555CDR accuracy specification. Comparator thresholds, propagation delay, leakage, capacitor temperature and voltage behavior, board parasitics and the measurement setup can add further effects. The purpose of the calculation is to show how much of the available margin may already be consumed before changing the timer.

Imagine that the equipment accepts pulses from 900Hz to 1,100Hz. The passive-only calculation leaves some margin, which the remaining error terms and tests must address. If the equipment instead needs 980Hz to 1,000Hz, the same passive selections already deserve attention before purchasing starts an alternate search. A tighter acceptance window does not become achievable merely because a second timer has the same nominal threshold ratios.

Those acceptance windows are hypothetical. In a real project, derive the limits from the function receiving the pulse: a display update, a test sequence, a timeout or another defined task. Preserve high and low interval limits if the receiving circuit cares about them separately. A frequency measurement alone can hide a duty-cycle problem.

It is often more productive to improve the timing capacitor specification, define the load and record the allowable interval than to collect a long list of nominally similar timers. That work can reveal margin problems in the current circuit before a substitution is even proposed. It also makes later comparison tests meaningful because the team knows which difference would actually cause a problem.

Four nearby timers, four separate engineering questions

A useful alternate list creates options the team can evaluate. It does not promise that every listed part is interchangeable. The four candidates below are distinct timer families with publicly identifiable ordering codes. None has been qualified here as a replacement on an actual TLC555CDR board.

Table 4. Four comparison candidates for a TLC555CDR design.

Sources checked September 23, 2026. Product-page characteristics establish comparison value; they do not establish complete pin, footprint, timing or system compatibility.

The NE555DR comparison is useful where engineers are tempted to treat “555” as a complete specification. Its TI page describes operation from 5V to 15V. That already raises a concrete question for a board using the TLC555C at a lower voltage. Familiar function and familiar package do not resolve the supply difference. The actual load and power budget need their own review.

LMC555CMX/NOPB is a more natural place to investigate a low-power CMOS alternative. Its ordering page identifies the SOIC version and a wider temperature range. The procurement value comes from a real, specific candidate the engineer can evaluate, rather than an unspecified family reference. A wider listed range still does not prove matching behavior at the boundaries of the original circuit.

TLC551CD introduces a different practical concern: the identified ordering option is tube supplied. That may suit a prototype bench and complicate an automated production line. TI's page also contains recommendation-card wording about pinout that is not enough to certify compatibility. Keep it as a candidate until the exact package and electrical documentation are reconciled. A sales-page comparison label should never become the sole engineering release record.

TS555IDTTR adds a second manufacturer's CMOS timer to the discussion. ST's public page identifies the exact ordering option and SO-8 industrial grade. It creates a credible cross-vendor investigation, provided the team checks the package drawing, pin assignments, electrical conditions and assembled-board behavior. Supplier diversity is useful when the resulting circuit has actually been evaluated.

In practice, choose the candidate that best matches the difficult requirement first. For a low-voltage product, supply behavior may dominate. For a fixture running from a stable rail, output loading and pulse acceptance may matter more. For a long-running assembly program, carrier format and release documentation can be the immediate obstacle. The best investigation order follows the product's constraint, rather than a uniform ranking of timer brands.

Turn a supply signal into a purchase decision

Normal replenishment and a changed device need different work

If the approved TLC555CDR continues to meet the product's needs and the supplier can provide a suitable dated offer, the immediate work is ordinary replenishment. Confirm the code, carrier, required quantity, shipment plan and documentation. There is no engineering benefit in reopening a settled circuit solely because a new fab appears in the news.

A product change requires a different conversation. TI's published PCN process describes identifying affected products, the reason for change, anticipated impact, qualification information and projected production shipments. An applicable notice can therefore connect a manufacturing development to a specific device. The article has not established any TLC555CDR-to-SM1 transfer. Ask for the actual affected-product evidence if that relationship matters to your approval process. TI PCN information.

For an urgent order, state the use case before comparing quotes. A maintenance team needing a few devices can have different carrier needs from a contract manufacturer feeding a production run. The difference is logistical, but it can determine whether the offered material is usable on the intended date. Keep quantity, handling and traceability requirements visible alongside the exact part number.

Table 5. Choose the next action from the actual obstacle.

Source: TLC555 Rev. K, TI's exact-device and PCN information; procurement actions are YG GROUP's editorial recommendations.

Give an evaluation batch a specific job

An evaluation batch should answer the open engineering question. Before ordering it, write down the board revision, supply conditions, connected load and allowed timing window. For an alternate, verify pin assignment and footprint first, then define the power-up, steady-state and reset tests that matter. That sequence prevents a promising room-temperature waveform from becoming an unsupported production approval.

Keep the original device as a reference under the same setup when available. Use the same timing components and measurement points for a direct circuit comparison; document any intentional component changes separately. If the alternate requires a different capacitor, the engineering decision concerns the modified circuit as a whole. Record that fact rather than presenting the result as a chip-only comparison.

A basic test record can be concise: identify the board and samples, state the conditions, capture frequency and high/low intervals, and record the outcome against the specified limits. Add temperature, supply ramp or interference checks where the product requirement calls for them. The point is to produce evidence the next engineer can interpret, not a large report with an unexplained “pass.”

The same discipline helps purchasing avoid a false choice between unlimited safety stock and an immediate redesign. A documented alternate evaluation, a clear next-build requirement and a confirmed shipment can each solve a different part of the problem. Their usefulness depends on the actual schedule and application. No assumed lead time or inventory target is needed to recognize those options.

Keep the record useful at the next order

Save the approved ordering code and carrier with the BOM revision, not just in an email thread. Attach the relevant change decision and note which alternatives were evaluated, under what conditions, and with which circuit changes. A candidate that passed one board revision may need review after a power-rail or load change.

When the next factory announcement arrives, the team can then compare it with an established baseline. That turns broad industry news into a focused question for the manufacturer or supplier. It also keeps routine replenishment from inheriting assumptions made during an earlier urgent buy.

Make the next build easier to approve

Analog capacity news becomes useful when it helps the team decide what to buy, retain or evaluate. For TLC555CDR, that begins with an orderable device whose package, commercial-temperature range and carrier are understood. The current CDR/CD status distinction shows why the full code matters even inside a familiar timer family.

The engineering work is equally specific. Know the required supply and output load, define the allowed timing window, and separate passive tolerance from device and board effects. The RC example shows how a modest capacitor tolerance can consume meaningful timing margin before an alternate timer is considered. That observation is useful whether supply is comfortable or tight.

Use an alternate only after the actual circuit and assembly requirements support it. A smaller supplier list with clear evidence is more useful than several unqualified “equivalents.” Keep the existing design when it remains appropriate, investigate the most relevant fallback, and tie the next purchase to a dated commitment for the exact item.

For the next build, keep three things together: the approved BOM, its timing acceptance limits and the dated offer for the exact part.

References

• Texas Instruments, TLC555 CMOS Timer, SLFS043K, revised January 2026. Technical sections and package information; reviewed package addendum dated September 18, 2026.
• Texas Instruments, TLC555CDR exact ordering and package information. Checked September 23, 2026.
• Texas Instruments, Sherman, Texas: 300mm wafer fabs.
• Texas Instruments, Production begins at the Sherman manufacturing facility, December 17, 2025.
• Texas Instruments, Product change notification process.
• Texas Instruments, NE555DR exact ordering information.
• Texas Instruments, LMC555CMX/NOPB exact ordering information.
• Texas Instruments, TLC551CD exact ordering information.
• STMicroelectronics, TS555 product overview and TS555IDTTR ordering information.