FCom Fuji Crystal · FSF-5050 Series
400, 402, 403.55 & 408.5 MHz SAW Bandpass Filters
FSF-5050-400M · FSF-5050-402M · FSF-5050-403M55 · FSF-5050-408M5
Four frequency options in a 5.0 × 5.0 mm leadless SMD package, with model-specific bandwidth definitions, insertion loss, matching requirements and operating limits.
Model Selection
Compare the requirements that matter
Bandwidths below use different attenuation levels. Check the definition before comparing values or choosing a replacement. Shared package dimensions do not establish electrical or PCB interchangeability.
2 dB bandwidth
FSF-5050-400M
400 MHz
2 dB bandwidth 17 MHz min. / 21.4 MHz typ. — relative to ILmin
- Insertion loss (ILmin)
- 1.3 dB typ. / 2.8 dB max.
- Operating range
- −55 to +85 °C
- Source / load test
- 50 Ω single-ended
1 dB bandwidth
FSF-5050-402M
402 MHz
1 dB bandwidth 16 MHz min. / 18 MHz typ. — relative to ILmin
- Insertion loss (ILmin)
- 1.6 dB typ. / 3.0 dB max.
- Operating range
- −55 to +85 °C
- Source / load test
- 50 Ω single-ended
3 dB bandwidth · external matching
FSF-5050-403M55
403.55 MHz
3 dB bandwidth 1.15 MHz typ. — typical electrical center 403.59 MHz
- Insertion loss (ILmin)
- 2.4 dB typ. / 4.0 dB max.
- Operating range
- −40 to +85 °C
- Test system
- 50 Ω analyzer with external matching
- Device port impedance
- 346 Ω ∥ 3.8 pF each
2 dB bandwidth
FSF-5050-408M5
408.5 MHz
2 dB bandwidth 16 MHz min. / 20.8 MHz typ. — relative to ILmin
- Insertion loss (ILmin)
- 1.4 dB typ. / 2.8 dB max.
- Operating range
- 0 to +50 °C
- Source / load test
- 50 Ω single-ended
- Reference test temperature
- 25 °C
The 403.55 MHz model uses external matching and has a typical electrical center of 403.59 MHz. Its reference test part uses a different signal-pin arrangement, so its footprint must not be transferred directly into the FCom design. The bandwidth values above use 1 dB, 2 dB and 3 dB criteria and cannot be converted from one another using these numbers alone.
Six key parameters per model
Electrical specifications
“—” means not specified, not zero. Min., Typ. and Max. retain their supplied meanings. ILmin is the minimum passband insertion loss; it is not a guarantee of that loss across the entire bandwidth.
FSF-5050-400M
Scroll horizontally to view all columns.
| Parameter | Min. | Typ. | Max. | Unit | Definition / condition |
|---|---|---|---|---|---|
| Center frequency | — | 400.0 | — | MHz | Typical; mean of the frequencies at ILmin + 2 dB |
| Minimum insertion loss, ILmin | — | 1.3 | 2.8 | dB | Minimum passband insertion loss |
| 2 dB bandwidth | 17 | 21.4 | — | MHz | Relative to ILmin |
| Operating temperature | −55 | — | +85 | °C | Operating limits |
| Test source impedance | — | 50 | — | Ω | Test termination; not intrinsic device impedance |
| Test load impedance | — | 50 | — | Ω | Test termination; not intrinsic device impedance |
ILmin is the minimum passband insertion loss and is not a maximum-loss guarantee across the entire bandwidth. A reference measurement temperature and amplitude-ripple limit are not specified in the supplied data.
FSF-5050-402M
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| Parameter | Min. | Typ. | Max. | Unit | Definition / condition |
|---|---|---|---|---|---|
| Center frequency | — | 402.0 | — | MHz | Typical |
| Minimum insertion loss, ILmin | — | 1.6 | 3.0 | dB | Minimum passband insertion loss |
| 1 dB bandwidth | 16 | 18 | — | MHz | Relative to ILmin; not interchangeable with a 2 dB or 3 dB value |
| Operating temperature | −55 | — | +85 | °C | Operating limits |
| Test source impedance | — | 50 | — | Ω | Test termination; not intrinsic device impedance |
| Test load impedance | — | 50 | — | Ω | Test termination; not intrinsic device impedance |
A reference measurement temperature and amplitude-ripple limit are not specified in the supplied data. The bandwidth is measured 1 dB above ILmin.
FSF-5050-403M55
Scroll horizontally to view all columns.
| Parameter | Min. | Typ. | Max. | Unit | Definition / condition |
|---|---|---|---|---|---|
| Center frequency | — | 403.59 | — | MHz | Typical electrical center; nominal product frequency 403.55 MHz |
| Minimum insertion loss, ILmin | — | 2.4 | 4.0 | dB | 403.43–403.75 MHz |
| 3 dB bandwidth | — | 1.15 | — | MHz | Relative to ILmin; distinct from the specified passband intervals |
| Passband attenuation (typ.) | — | 2.0 | 3.0 | dB | 403.33–403.85 MHz; relative to ILmin |
| Passband attenuation (typ.) | — | 3.0 | 6.0 | dB | 403.27–403.91 MHz; relative to ILmin |
| Operating temperature | −40 | — | +85 | °C | Operating limits; not the reference test temperature |
Nominal product frequency: 403.55 MHz. Typical electrical center: 403.59 MHz. Electrical data use a 25 °C reference temperature and external matching; the operating range is a separate limit. Specified passband attenuation is relative to ILmin and is not an amplitude-ripple specification. Device port impedance is specified as 346 Ω in parallel with 3.8 pF; the matched measurement system terminates each device port into 50 Ω through a 47 nH series inductor and an 8 pF shunt capacitor to ground on the analyzer side of the inductor.
FSF-5050-408M5
Scroll horizontally to view all columns.
| Parameter | Min. | Typ. | Max. | Unit | Definition / condition |
|---|---|---|---|---|---|
| Center frequency | — | 408.5 | — | MHz | Typical; mean of the frequencies at ILmin + 2 dB |
| Minimum insertion loss, ILmin | — | 1.4 | 2.8 | dB | Minimum passband insertion loss |
| 2 dB bandwidth | 16 | 20.8 | — | MHz | Relative to ILmin |
| Operating temperature | 0 | — | +50 | °C | Operating limits |
| Test source impedance | — | 50 | — | Ω | Test termination; not intrinsic device impedance |
| Test load impedance | — | 50 | — | Ω | Test termination; not intrinsic device impedance |
Electrical data use a 25 °C reference temperature; the operating range is a separate limit. ILmin is the minimum passband insertion loss and is not a maximum-loss guarantee across the entire bandwidth. No amplitude-ripple limit is specified.
Stopband attenuation is absolute, referenced to 0 dB, for 400M, 402M and 408M5. For 403M55, passband and stopband attenuation are relative to ILmin. Consult the full model-specific data in the combined FCom PDF for additional attenuation bands and maximum ratings.
Application Fit
Typical applications
RF signal selection
Filter signals around the selected 400, 402, 403.55 or 408.5 MHz frequency when the signal bandwidth fits the applicable passband limits.
Receiver front ends
Provide bandpass filtering before subsequent receiver stages. Evaluate the specified rejection bands together with insertion loss and the system noise budget.
Custom RF / IF paths
Use in a custom signal path when the frequency, bandwidth definition, temperature limits and matching requirements meet the design needs.
Integration Notes
Matching, interfaces and PCB evaluation
400 / 402 / 408.5 MHz
Measurements use 50 Ω source and 50 Ω load terminations. These values describe the test system, not the intrinsic device impedances. The reference measurement circuits show direct connections without external matching networks.
Do not assume the same result for every PCB or source/load environment. Check layout parasitics and loading against the applicable FCom specification.
403.55 MHz
The supplied FCom test configuration uses external matching at each port: a 47 nH series inductor and an 8 pF shunt capacitor to ground on the analyzer side of the inductor.
At the center frequency, each device port is specified as 346 Ω in parallel with 3.8 pF. The matched measurement system terminates each port into 50 Ω at a 25 °C reference temperature. Evaluate the network with the applicable FCom pin assignment and actual PCB parasitics.
Use the FCom pin assignment. The 403.55 MHz reference part uses a different signal-pin arrangement; its pin numbering and footprint must not be transferred directly to FSF-5050-403M55.
Mechanical Interface
Package & pin assignment
The supplied FCom pages show a 5.0 × 5.0 mm, 8-pad leadless SMD package with a maximum height of 1.5 mm for all four models. Use the applicable FCom drawing in the combined datasheet for pad dimensions and confirm the mounting view before PCB release.
Shared FCom package
Product photographs identify the devices and the pad sides; they do not define pad orientation or pad 1 location. Confirm the mounting view and pad numbering against the applicable FCom drawing before PCB release.
FCom labels pins 2 and 6 Input/Output. Confirm the required signal direction for the selected configuration and contact FCom for other pin-configuration requirements.
| Pin(s) | FCom function |
|---|---|
| 2 | Input/Output |
| 6 | Input/Output |
| 1, 3 | Ground |
| 5, 7 | Ground |
| 4 | Case ground |
| 8 | Case ground |
Selection and Design-In Support
What to include in your inquiry
Share the selected model, required bandwidth and its definition, source/load conditions and operating temperature. Include sample quantity and estimated usage so your request can be reviewed against the appropriate model configuration.
Confirm the applicable production specification and full ordering code before design release. For FSF-5050-403M55, include the proposed matching network and pin configuration.
Engineering Questions
Frequently asked questions
Can I compare the bandwidth numbers directly?
Use the attenuation level as well as the bandwidth value. FSF-5050-402M specifies 1 dB bandwidth; FSF-5050-400M and FSF-5050-408M5 specify 2 dB bandwidth; FSF-5050-403M55 specifies 3 dB bandwidth. All are relative to ILmin, but they are different definitions and cannot be converted from these values alone.
Why does the 403.55 MHz model list a 403.59 MHz center?
403.55 MHz is the nominal product frequency and the marking used to identify FSF-5050-403M55. The supplied electrical table lists 403.59 MHz as the typical center frequency at the 25 °C reference temperature. Keep these two values distinct when assessing the signal band.
Does the 403.55 MHz model need external matching?
The supplied FCom test configuration uses a 50 Ω source and load with a 47 nH series inductor at each port and an 8 pF shunt capacitor on the analyzer side of each inductor. Device input and output impedances at the center frequency are each specified as 346 Ω in parallel with 3.8 pF. Verify the matching layout with the applicable FCom pin assignment.
Are the four models interchangeable on the same PCB?
Interchangeability is not established. Check frequency, bandwidth definition, insertion loss, matching and temperature range. The supplied FCom pages use signal pins 2 and 6, while the 403.55 MHz reference part uses a different signal-pin arrangement. Do not copy that reference footprint or pin numbering into the FCom design.
Are all specifications measured at 25 °C?
A 25 °C reference temperature is stated for FSF-5050-403M55 and FSF-5050-408M5. The supplied 400 MHz and 402 MHz data do not state a reference measurement temperature. Operating temperature ranges are separate limits and should not be treated as measurement conditions.
What should I provide for selection and ordering?
Provide the selected model or frequency, required bandwidth and its 1 dB, 2 dB or 3 dB definition, source and load requirements, operating temperature, sample quantity and estimated usage. Confirm the applicable production specification, pin configuration and complete ordering code with FCom.