SI2457-D-GT - 56 kbps ISOMODEM | Skyworks Solutions
MPN: SI2457-D-GT ✓ ActiveSI2457-D-GT Overview
An ISOMODEM is a semiconductor implementation of a modem's modulation, demodulation, and protocol functions. It belongs to the modem IC hierarchy, integrates data-link signaling with a host-facing controller interface, and is commonly positioned between a host processor and a telephone or data-network interface. Its primary design purpose is to reproduce standardized modem signaling without requiring a discrete modem subsystem.
The SI2457-D-GT supports data rates from Bell 300 bps through 56 kbps, automatic rate negotiation, Type I and Type II caller-ID decoding, and parallel, UART, or SPI host interfaces. Its on-chip program ROM provides the firmware for the documented features, while program RAM permits minor firmware changes. Flexible clocking includes a low-cost 32.768 kHz oscillator option and a 4.915 MHz clock option.
The device includes global capacitive isolation rated at more than 6,000 V and parallel phone detection. These characteristics allow the modem circuitry to interface with a telephone line while maintaining separation between line-side and logic-side functions. The SI2457 family is intended for interoperable data communications where V-series protocols, caller identification, and a compact controller implementation are required.
Typical uses include embedded modems, fax equipment, data terminals, industrial communication equipment, and telephone-line data products. Designers should select the interface mode and clock arrangement that match the host controller and line interface, and should use the manufacturer pin-description table when assigning PCB nets.
A key design consideration is that a shared 24-pin TSSOP footprint does not by itself guarantee firmware-level interchangeability. Review the protocol list, clock requirements, interface selection, isolation implementation, and exact orderable suffix before treating another device as a replacement.
This page combines the manufacturer's Revision D family datasheet, distributor identification, supported protocol details, package information, and practical replacement criteria to support component selection, PCB planning, and sourcing.
Drop-in alternatives for SI2457-D-GT — same package, pin-to-pin compatible. Different-package parts requiring PCB rework are excluded.
SI2457-C-GTR
✅ Drop-In📋 Reference alternative (not in catalog)
SI2457-C-GT
✅ Drop-InContact for price
View Datasheet →SI2457-D-GT Specifications
| Device Type | 56 kbps system-side ISOMODEM |
| Supply Voltage | 3.3 V |
| Maximum Data Rate | 56 kbps |
| Minimum Modem Data Rate | 300 bps |
| Supported ITU-T Formats | V.21, V.22, V.23, V.32, V.34, V.90 |
| Supported Bell Formats | Bell 103, Bell 212A |
| Additional Protocol Support | V.42, V.42bis, V.44, Fast Connect, MNP2-5 |
| Caller ID Support | Type I and Type II decode |
| Host Interface Options | UART, SPI, or parallel |
| External Memory Requirement | No external ROM or RAM required |
| Program Memory | On-chip program ROM and program RAM |
| Low-Speed Clock Option | 32.768 kHz |
| High-Speed Clock Option | 4.915 MHz |
| Capacitive Isolation | Over 6000 V |
| Telephone Line Detection | Parallel phone detect |
| Package | 24-pin TSSOP |
| Package Type | Gull-wing TSSOP |
| Terminal Count | 24 |
| Operating Temperature Range | 0 C to 70 C |
| Mounting Type | Surface mount |
| RoHS Status | Compliant |
SI2457-D-GT gull-wing tssop Pin Configuration Guide
Pin configuration for SI2457-D-GT (gull-wing tssop package). Pin numbering, functions, and connection diagrams are defined in the manufacturer datasheet. Refer to it for the exact footprint and soldering guidelines.
No detailed pinout data available for SI2457-D-GT.
Refer to the datasheet for full pin configuration.
Typical Applications
SI2457-D-GT is suitable for 6 applications: Embedded 56 kbps Data Modem, Caller-ID Telephone Equipment, Industrial Data Terminal, Legacy Fax and Data Endpoint, Automated Rate-Negotiation System, Telephone-Line Network Interface.
Embedded 56 kbps Data Modem
The SI2457-D-GT fits embedded modem designs requiring a complete 56 kbps V-series signaling engine in a 24-pin TSSOP. Its support for V.21, V.22, V.23, V.32, V.34 and V.90, together with Bell 103 and Bell 212A formats, allows a host processor to communicate over legacy telephone or data-service lines. On-chip program ROM and RAM reduce external memory requirements, while UART, SPI, and parallel interfaces provide design flexibility. The designer must confirm the required protocol set, clock source, and host firmware against Revision D before production release.
Recommended
Caller-ID Telephone Equipment
Type I and Type II caller-ID decoding make the SI2457-D-GT suitable for telephone equipment that receives and forwards caller information to an embedded controller. Its modem formats extend from Bell 300 bps through 56 kbps, enabling the same device to support signaling and caller-ID handling within a compact design. A 3.3 V supply and 24-pin TSSOP package simplify integration into telephone terminals and multifunction communications products. The host software must correctly transfer decoded identifiers, and the line-side network must satisfy the isolation and telephone-interface requirements described by the manufacturer.
Recommended
Industrial Data Terminal
The SI2457-D-GT can serve as the modem engine in an industrial data terminal designed around legacy switched-network or telephone-line connectivity. Its 56 kbps maximum rate, automatic rate negotiation, and support for V.42bis error correction and MNP2-5 provide a practical protocol combination for reliable compressed data transfer. The 0 C to 70 C operating range is suitable for many commercial and industrial enclosure environments, although it does not establish automotive or extreme-environment qualification. Select the host interface and clock arrangement according to the controller platform and validate line coupling, isolation, and restart behavior.
Recommended
Legacy Fax and Data Endpoint
Legacy fax and data endpoints can use the SI2457-D-GT when the equipment still requires V-series modem interoperability rather than an all-digital communications interface. Support for V.21, V.22, V.23, V.32, V.34 and V.90 provides several signaling rates, while V.42, V.42bis and Fast Connect options improve compatibility with contemporary modem negotiation procedures. The 24-pin TSSOP package supports compact terminal construction, and the device requires no external ROM or RAM. The equipment designer should verify the exact V.29 configuration and any application-specific timing required by the target fax or data protocol.
Recommended
Automated Rate-Negotiation System
MNP2-5 automatic rate negotiation allows the SI2457-D-GT to work in systems where the connected modem must establish a supported rate during call setup. This is useful for unattended data equipment that must operate across variable line conditions and negotiate with remote V-series equipment. The IC combines modem signaling and protocol support in one 24-pin TSSOP, while flexible 32.768 kHz and 4.915 MHz clock options help match different circuit arrangements. Firmware, clock selection, and line-network calibration must be validated together to obtain reliable negotiation and throughput across supported connection types.
Recommended
Telephone-Line Network Interface
The SI2457-D-GT is appropriate for a telephone-line interface requiring modem modulation, demodulation, and protocol handling close to the host controller. Its global capacitive isolation rated at more than 6,000 V and parallel phone detection help structure a line-facing design that remains separated from logic circuitry. The 3.3 V device provides UART, SPI, or parallel connectivity to the system controller, and the on-chip program memory removes external ROM or RAM from the modem subsystem. Engineers should follow the manufacturer network recommendations closely because isolation voltage alone does not validate the complete telephone-interface safety or regulatory performance.
Recommended
Recommended Products Summary
Engineering reference data for SI2457-D-GT — comparison, design guidance, and compliance information.
Selection Guide
Comparison with Alternatives
| Parameter | This Product | SI2457-C-GTR | SI2457-C-GT |
|---|---|---|---|
| Package | 24-pin TSSOP | 24-pin TSSOP | 24-pin TSSOP |
| Brand | Skyworks Solutions Inc. | Silicon Laboratories | Silicon Laboratories |
| Maximum Data Rate | 56 kbps | 56 kbps | 56 kbps |
| Supported Modem Formats | ITU-T V.21, V.22, V.23, V.32, V.34, V.90; Bell 103, Bell 212A | V.21, V.22, V.23, V.32, V.34, V.90, Bell 103, Bell 212A | V.21, V.22, V.23, V.32, V.34, V.90, Bell 103, Bell 212A |
Key Differentiators
- Maintains the same 56 kbps headline data rate as the documented replacements (vs SI2457-C-GTR)
- Provides a 24-pin TSSOP replacement path without changing the package (vs SI2457-C-GT)
- Revision D family documentation identifies MNP2-5 and V.42bis support (vs SI2457-C-GT)
Design Notes
Assign every net from the manufacturer pin-description table before layout begins, particularly the telephone-line, capacitive-isolation, clock, and host-interface signals. The 24-pin TSSOP footprint leaves limited escape space around the device, so place the isolation and line-network components away from the host connector while preserving the shortest practical isolation path. Do not infer pin functions from a generic 16-pin modem symbol because the SI2457-D-GT is identified as a 24-pin TSSOP device.
Decouple the 3.3 V modem supply locally and keep return-current paths short. Place the input capacitor and additional high-frequency bypass capacitor close to their corresponding supply pins, with a continuous ground reference beneath the device where the package and board construction permit. The listed specification establishes the 3.3 V operating supply but does not provide a recommended capacitance value, so use the values and layout guidance in the manufacturer datasheet and reference materials rather than estimating them from another modem.
Confirm the clock configuration before committing the printed circuit board because the family supports 32.768 kHz and 4.915 MHz options. Also verify whether the selected firmware expects UART, SPI, or parallel control signals. A replacement that retains the 24-pin package and 56 kbps headline rate can still require different initialization or timing. Review the exact orderable revision, supported V-series modes, caller-ID behavior, and program-memory behavior as a single compatibility checklist.
Keep the modem clock and host-interface traces away from the telephone-line network where practical, and preserve the manufacturer's isolation arrangement between line-side and logic-side circuitry. More than 6,000 V of capacitive isolation is a device capability rather than proof that the finished interface meets applicable product-safety requirements. Review creepage, clearance, surge exposure, grounding, and shield strategy for the target installation because those system-level constraints are not fixed by the IC package alone.
Compliance Information
RoHS compliance is stated in component records. The device is an interface modem IC rather than an automotive-qualified component, and no additional compliance claims are included.