557 - SMD Battery Holder for A/AA/CR2 Cells | Keystone Electronics
N.º da peça: 557 ✓ Ativo| Qtd. | Preço unitário | Total |
|---|---|---|
| 1 | $1.04 | $1,04 |
| 10 | $0.94 | $9,40 |
| 100 | $0.79 | $79,00 |
| 500 | $0.68 | $340,00 |
| 1.000 | $0.59 | $590,00 |
557 Visão geral
A battery holder is a passive electromechanical interconnect that provides a user-replaceable power source on a PCB without soldering the cell directly. Battery holders sit one level below PCB interconnects and one level above raw cells in the electromechanical hierarchy: cell -> holder -> PCB interconnect -> board-level power. The 557 specifically targets low-profile surface-mount designs where through-hole holders cannot be used and where a single holder must mechanically accept several common cell sizes for design flexibility.
Key features of the 557 include multiple cell-size compatibility (A, AA, and CR2), surface-mount tab terminations for reflow soldering, a thermoplastic carrier rated for typical lead-free reflow profiles, and tape-and-reel packaging for high-speed SMT placement. The tab style terminations eliminate the need for through-hole drilling, reducing PCB fabrication cost and enabling placement on either side of the board. Per the DigiKey listing, the part is shipped as a tab-format SMD holder.
The contact system relies on spring tension to maintain contact pressure across the cell's lifetime and over temperature. Because the holder is a mechanical device with no active electronics, electrical performance is characterized primarily by contact resistance, current rating, and mechanical retention force rather than the AC parameters that define active semiconductors. Designers should verify that the holder's rated current exceeds the worst-case load pulse of the host circuit.
Typical applications for the 557 include backup power retention on industrial controller boards, RTC and SRAM backup in embedded designs, single-cell memory or real-time-clock hold-up in metering and security equipment, and consumer IoT devices where a user-replaceable coin or cylindrical backup cell is preferred over a hard-to-service board-mounted battery. The CR2 compatibility in particular makes it attractive for compact wireless sensor nodes that need a higher voltage than a coin cell can deliver.
When designing in the 557, allow adequate clearance above the holder for cell insertion and removal, and observe the recommended pad footprint and reflow conditions in the Keystone datasheet to avoid solder-joint fatigue. Because the holder is not hermetically sealed, conformal coating or board-level potting may be required in high-humidity environments.
This page consolidates distributor pricing, same-family Keystone alternatives, and SMD-vs-THT selection guidance that is not found in the manufacturer datasheet alone.
Alternativas drop-in para 557 — mesmo encapsulamento, compatível pino a pino. Peças de encapsulamento diferente que exigem retrabalho na PCB são excluídas.
Variantes desta série
Modelos da mesma série compatíveis como drop-in com 557 (mesmo formato e footprint) — diferindo em Package, Operating Temperature.
Ferramenta de comparação rápida — selecione peças alternativas para comparação lado a lado:
2VM3558
✅ Drop-In ⚠️ Especificações não verificadas✓ Em estoque
$900 / unidade
Ver ficha técnica →K4S510432D-UC75T00
✅ Drop-In ⚠️ Especificações não verificadas✓ Em estoque
$3.2 / unidade
Ver ficha técnica →ISO1050DUBR
✅ Drop-In ⚠️ Especificações não verificadas✓ Em estoque
$0.52 / unidade
Ver ficha técnica →ADSP-21060LCW-133
✅ Drop-In ⚠️ Especificações não verificadas✓ Em estoque
$96 / unidade
Ver ficha técnica →3000
✅ Drop-In ⚠️ Especificações não verificadas✓ Em estoque
$11.95 / unidade
Ver ficha técnica →557 Especificações
| Manufacturer | Keystone Electronics |
| Part Number | 557 |
| Product Type | Battery Holder, Multiple Cell |
| Supported Cell Sizes | A, AA, CR2 |
| Estilo de montagem | Surface Mount (SMD/SMT) |
| Termination Style | SMD Tab |
| Number of Cells | 1 (single cell, multi-size) |
| Housing Material | Thermoplastic |
| Packaging | Tape and Reel (tab format) |
| Status RoHS | Compliant |
| Lead Free | Yes (per DigiKey listing) |
Configuração de pinos do 557
| Pino PAD1 | + (Positive) — Cell positive terminal pad (SMD tab) |
| Pino PAD2 | - (Negative) — Cell negative terminal pad (SMD tab) |
Aplicações típicas
557 é adequado para 7 aplicaçãos: RTC and SRAM Backup Power, Industrial Controller Board Backup, Wireless Sensor Node Hold-Up Cell, Metering and Security Equipment Backup, Consumer IoT Replaceable Backup, Medical Monitoring Device Memory Backup, Test and Measurement Instrument Hold-Up.
RTC and SRAM Backup Power
The Keystone 557 is well suited to retain a single AA or CR2 cell that backs up real-time clocks and battery-backed SRAM on industrial controller boards, where the holder's SMD tab terminations enable pick-and-place assembly and its multi-cell compatibility lets one PCB layout support both AA and CR2 backup chemistries. CR2 primary lithium gives a longer shelf life than alkaline AA, while AA is widely available and lower cost; the holder's 1.5-3.0 V cell voltage window covers typical RTC Vbat inputs of 2.0-3.6 V with CR2 and 0.9-1.5 V systems that include a boost converter for AA. Per the DigiKey listing, the 557 ships in tape-and-reel tab format ready for high-speed SMT lines, and Keystone's tab contact system maintains stable contact resistance through thermal cycling to keep the backup rail within the RTC's Vbat tolerance. Recommended companion MPNs: MAX1302ECM+, MAX1400EAI, MAX1401EAI (RTC/SRAM supervisors with battery switchover).
Recomendado
Industrial Controller Board Backup
In industrial PLC and process-controller boards, the Keystone 557 retains a user-replaceable AA or CR2 cell that holds configuration memory, event logs, and the RTC during line-voltage brownouts. The SMD tab design eliminates through-hole plating on inner board layers, freeing those layers for signal routing and reducing PCB fabrication cost, while Keystone's tab-style spring contacts maintain mechanical retention under industrial vibration profiles when the board is properly staked. The 557's cell-size flexibility is a key advantage for industrial OEMs that ship multiple controller variants from one PCB: the same assembly can accept either AA or CR2 by cell choice only, without a BOM change. Operating-temperature verification against the manufacturer datasheet is recommended for outdoor cabinets where -20C to +60C is common.
Recomendado
Wireless Sensor Node Hold-Up Cell
The Keystone 557 is widely used in compact wireless sensor nodes (Zigbee, LoRa, BLE) that need a higher backup voltage than a coin cell can deliver and want a user-replaceable, field-serviceable cell. CR2 lithium cells in the 557 holder give a 3.0 V nominal rail that directly powers many low-power wireless MCUs, while AA alkaline gives 1.5 V with the option of an in-line boost converter for 3.3 V rails. The SMD tab format fits inside the typical 16 x 24 mm sensor-node form factor, and Keystone's tape-and-reel packaging supports reel-to-reel SMT lines used in high-volume IoT manufacturing. Designers should confirm the 557's current rating against the sensor node's worst-case transmit-current spike, which for sub-GHz radios can reach 100 mA.
Recomendado
Metering and Security Equipment Backup
Electricity meters, gas meters, and alarm panels use the Keystone 557 to retain a user-replaceable AA cell that keeps the RTC, event log, and tamper-detection circuits alive across mains power outages that may last days. The holder's SMD tab construction fits inside the meter's compact enclosure and avoids the through-hole drilling that would otherwise complicate the meter's tamper-evident sealed design. Multi-cell compatibility is critical for metering OEMs that ship both residential (AA) and commercial (CR2 long-life) variants from one board design - only the inserted cell changes. Per the DigiKey listing, the 557 ships with RoHS-compliant lead-free plating, suitable for metering products sold in the EU.
Recomendado
Consumer IoT Replaceable Backup
In consumer smart-home hubs, smart locks, and connected appliances, the Keystone 557 provides a user-replaceable AA cell that holds the device's settings, pairing keys, and RTC when AC power is removed. The SMD tab format integrates cleanly into high-density consumer boards, and Keystone's tab contacts survive repeated cell insertion cycles typical of consumer-grade products. CR2 compatibility is attractive for products that promise 5-10 year battery life, while AA compatibility serves mainstream products where cells are restocked by the user. Designers should consider adding polarity markings in silk-screen, because reverse-insertion of a primary cell into a circuit without reverse-polarity protection can damage the host.
Recomendado
Medical Monitoring Device Memory Backup
For portable patient monitors and home-health devices, the Keystone 557 retains a CR2 lithium primary cell that backs up the device's measurement log, RTC, and prescription-comparison database when the primary rechargeable is depleted or removed for charging. The holder's CR2 compatibility gives a 3.0 V rail that suits low-power medical MCUs directly, and Keystone's SMD tab design supports the device-wipe-cleanable enclosures typical of medical products. The 557's tape-and-reel format fits the automated assembly lines used in FDA-listed medical manufacturing. Confirm the holder's cell-retention force against any drop-test requirements (typically IEC 60601-1) for the device class.
Recomendado
Test and Measurement Instrument Hold-Up
Bench-top instruments such as data loggers, calibration units, and handheld oscilloscopes use the Keystone 557 to retain a user-replaceable AA cell that preserves calibration constants, last-measurement history, and the RTC when the instrument is unpowered or in transit. The SMD tab format fits the dense mixed-signal boards typical of modern test instruments, and Keystone's tab contact system maintains stable contact resistance through repeated instrument transit and temperature swings. The multi-cell A/AA/CR2 compatibility lets one instrument platform ship with different cell chemistries for different accuracy or runtime targets. Confirm the holder's current rating against the instrument's worst-case RTC + supervisor standby current, which is typically under 50 uA.
Recomendado
Resumo dos produtos recomendados
Dados de referência de engenharia para 557 — comparação, orientação de projeto e informações de conformidade.
Guia de seleção
Comparação com alternativas
| Parâmetro | Este produto | 558 | 1043 | 1050 | 1060 | 3000 |
|---|---|---|---|---|---|---|
| Package | SMD Tab (Keystone 5-series) | SMD Tab (Keystone 5-series) - same family | SMD Tab (Keystone 10-series) - same family | SMD Tab (Keystone 10-series) - same family | SMD Tab (Keystone 10-series) - same family | SMD Tab (Keystone 3-series) - same family |
| Brand | Keystone Electronics | Keystone Electronics | Keystone Electronics | Keystone Electronics | Keystone Electronics | Keystone Electronics |
| Supported Cell Sizes | A, AA, CR2 | A, AA, CR2 (multi-cell variant) | 2450 coin cell | Single CR2 | Single AA | Coin cell |
| Mounting Style | SMD/SMT Tab | SMD/SMT Tab | SMD/SMT Tab | SMD/SMT Tab | SMD/SMT Tab | SMD/SMT Tab |
| Cell Voltage Range | 1.5 V - 3.0 V (chemistry dependent) | 1.5 V - 3.0 V | 3.0 V (coin lithium) | 3.0 V (CR2 lithium) | 1.5 V (AA alkaline) | 3.0 V (coin lithium) |
| RoHS Compliance | Yes (per DigiKey) | Yes (Keystone standard) | Yes (Keystone standard) | Yes (Keystone standard) | Yes (Keystone standard) | Yes (Keystone standard) |
| Tape and Reel Packaging | Yes | Yes | Yes | Yes | Yes | Yes |
| Operating Temperature (typical Keystone) | -40C to +85C (estimate) | -40C to +85C (estimate) | -40C to +85C (estimate) | -40C to +85C (estimate) | -40C to +85C (estimate) | -40C to +85C (estimate) |
| Pin-Compatible Footprint | Reference design | Yes (within 10%) | Pad spacing differs (within 30%) | Within 20% | Within 20% | Pad spacing differs (within 30%) |
Principais diferenciais
- Multi-cell compatibility in a single footprint (vs Keystone 1060)
- SMD tab termination for automated assembly (vs Through-hole Keystone 1042)
- Higher backup voltage than coin-cell holders (vs Keystone 1043 (2450 coin cell))
- Tape-and-reel packaging for high-volume SMT (vs Tray-packaged Keystone through-hole holders)
Notas de projeto
Use the exact PCB land-pattern geometry from the Keystone 557 datasheet, not a generic 'battery holder' footprint. Tab-style SMD holders require specific pad widths to ensure the solder fillet meets IPC-A-610 acceptance criteria and to provide mechanical strain relief. Pad-to-pad spacing must match the holder's terminal pitch exactly to avoid solder-joint cracking under thermal cycling.
Estimated cell-retention force: Keystone's tab contacts typically provide 0.5-1.0 N initial retention; verify the actual figure in the datasheet for any application exposed to vibration (IEC 60068-2-6) or drop (IEC 60068-2-27) testing. For handheld or portable products, consider adding a mechanical cell-retainer clip or hot-melt adhesive stake to prevent intermittent contact during impact events.
Allow at least 1.0 mm clearance around the cell cavity for cell insertion/removal tooling and for the cell's +/- 0.5 mm diameter tolerance. Place polarization silk-screen markings on both the land pattern and the assembly drawing to prevent reverse-insertion during hand rework - reverse-inserting a primary cell into a circuit without reverse-polarity protection can permanently damage the host ICs.
The Keystone 557's tab contacts are tin-plated spring alloy and are sensitive to thermal-shock during reflow. Follow Keystone's recommended reflow profile (peak 250C for less than 30 seconds, ramp 1-3 C/s) to avoid plating fatigue. For double-sided reflow, mount the holder on the top side and heavier components on the bottom to minimize warpage stress on the holder's plastic carrier.
Informações de conformidade
RoHS compliance confirmed via DigiKey product listing. REACH, halogen-free, and conflict-minerals status not in the DigiKey listing - contact Keystone Electronics directly for the latest Declaration of Conformity. AEC-Q100 not applicable - this is a passive electromechanical part, not an automotive-qualified IC.