PFS7728H

Key Specs

Spec	Value	Condition	Source
Mode	Continuous Conduction (CCM)		Digi-Key
Switching Frequency (Typ)	22kHz ~ 123kHz		Digi-Key
Voltage Supply	10.2V ~ 15V		Digi-Key
Operating Temperature Range	-40°C ~ 150°C (TJ)		Digi-Key
Mounting Type	Through Hole		Digi-Key
Package Case	16-SSIP, 13 Leads, Exposed Pad, Formed Leads		Digi-Key
Supplier Device Package	eSIP-16D		Digi-Key

When To Use

1. Universal input PFC front end → 385 VDC @ 100 W: The PFS7728H supports input voltages up to 305 VAC steady-state and 410 VAC abnormal conditions, making it suitable for universal line PFC applications. Its >95% typical efficiency and power factor >0.95 ensure compliance with power quality standards, unlike a generic non-PFC controller which would fail power factor requirements and cause excessive harmonic distortion.

2. Industrial motor drive auxiliary supply → 12 V @ 10 A peak: With peak output power ratings up to 450 W (high-line package) and continuous power up to 385 W, the PFS7728H can handle transient loads without thermal runaway. A synchronous buck controller lacking the integrated PFC stage would fail to meet input voltage range and power factor specs, potentially causing overcurrent and shoot-through in the boost stage.

3. High ambient temperature environment, -40°C to 150°C TJ → 100 W output: The thermal ratings and junction temperature range of -40°C to 150°C allow operation in harsh environments without latch-up or thermal shutdown. Alternative controllers with lower TJ max or less robust packages risk early thermal failure or erratic switching behavior under these conditions.

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When Not To Use

1. Output current > 30 A continuous: The PFS7728H’s maximum continuous output power tops out at 385 W in the high-line packages, corresponding roughly to 10–15 A depending on voltage. For higher currents, use a multi-phase buck controller designed for balanced current sharing and reduced thermal stress.

2. Quiescent current critical for battery-powered applications: With typical no-load consumption around 60 mW and standby currents in the 100s of mA, this device is unsuitable for μA-level sleep loads. Use a low-IQ PFM buck controller optimized for ultra-low quiescent current.

3. Switching frequency > 500 kHz required: The PFS7728H’s switching frequency range maxes at 123 kHz typical, with no support above 1 MHz. For compact magnetics or EMI-sensitive designs needing >500 kHz, a high-frequency buck controller is required.

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Application Notes

• The switching node (SW) carries high di/dt currents up to 7.5 A peak and must have a low-inductance layout with solid copper pours and minimal loop area to prevent EMI and voltage ringing.

• the REF pin, 6 (FB), and the PG pin are noise-sensitive and should be routed away from the switching node and high-current traces. Use separate ground returns for signal ground (pin 3, G) and power ground to minimize interference.

• The exposed pad must be soldered directly to the PCB ground plane with multiple thermal vias to maintain junction temperature below 150°C TJ max during peak load.

• Reference-pin capacitor (REF) requires a 0.1 µF ±20% ceramic capacitor placed as close as possible to the pin to stabilize internal references and prevent erratic switching frequency modulation.

• The power good (PG) pin output has a deglitch filter of ~81 ms; systems relying on power good signaling must accommodate this delay in startup sequencing.

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Pin numbers are package-specific. Verify against the datasheet pinout diagram before routing.

Gotchas

1. [Incorrect capacitor ESR assumption on output]: Assuming any high-value electrolytic on the PFC output is fine leads to instability and output voltage ripple beyond spec. The PFS7728H requires low-ESR capacitors rated for 450 V continuous to maintain stable feedback and prevent oscillations visible on the FB pin waveform. Fix by verifying capacitor ESR and using high-quality film or low-ESR electrolytics matching datasheet recommendations.

2. [Start-up sequencing with undervoltage locking]: Designers may assume the PFS7728H will start immediately at input voltages near the brown-in threshold (400 V). In practice, undervoltage lockout and brown-in delay cause the device to hold off switching, appearing dead on startup. Fix by monitoring input voltage ramp and ensuring bias voltage exceeds 10.2 V minimum with stable startup conditions.

3. [High impedance feedback resistor divider sensitivity]: Using resistor values outside the specified 8 MΩ to 16 MΩ range for the feedback divider leads to inaccurate output voltage sensing and potential overvoltage faults or premature shutdown. This manifests as erratic output voltage or repeated power good deassertion. Fix by adhering to the recommended resistor ratio and tolerance limits.

4. [Switching frequency variation due to reference capacitor tolerance]: The switching frequency can vary significantly if the REF pin capacitor deviates from the 0.1 µF ±20% spec, causing EMI filter design failures or thermal stress from frequency drift. Fix by choosing stable X7R or better ceramic capacitors and measuring frequency at test points during validation.