Key Specs
| Spec | Value | Condition | Source |
|---|---|---|---|
| Control Features | - | Digi-Key | |
| Current Quiescent IQ | 10 mA | Digi-Key | |
| Input Voltage (Max) | 18V | Digi-Key | |
| Mounting Type | Surface Mount | Digi-Key | |
| Number Of Regulators | 1 | Digi-Key | |
| Operating Temperature Range | -40°C ~ 125°C (TJ) | Digi-Key | |
| Output Configuration | Positive | Digi-Key | |
| Output Current (Max) | 1A | Digi-Key | |
| Output Type | Fixed | Digi-Key | |
| Output Voltage (Max) | - | Digi-Key | |
| Output Voltage (Min) | 5V | Digi-Key | |
| Package Case | TO-243AA | Digi-Key | |
| Protection Features | Over Temperature | Digi-Key | |
| Psrr | 70dB (120Hz) | Digi-Key | |
| Supplier Device Package | SOT-89 | Digi-Key | |
| Voltage Dropout (Max) | 1.4V @ 1A | Digi-Key |
When To Use
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12V → 5V @ 1A linear rail: The 18V maximum input voltage and 1A maximum output current rating suit a 12V to 5V step-down where dropout voltage up to 1.4V at full load is acceptable. Switching regulators in this scenario risk complexity and EMI; a lower current linear regulator would overheat and enter thermal shutdown rapidly.
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Post-switching regulator cleanup for noise-sensitive analog: The 70dB PSRR at 120Hz makes this part ideal to clean up switching ripple from a noisy buck output at moderate currents. Using a switching regulator alone risks injecting ripple into sensitive analog circuits, causing measurement errors or audio artifacts.
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Single positive fixed 5V rail in harsh thermal environment: The -40°C to 125°C junction rating and built-in over-temperature protection enable use in automotive or industrial control boards. A regulator lacking thermal protection could suffer thermal runaway under continuous high ambient temperature and load.
When Not To Use
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Battery-powered sensor node at μA sleep current: Quiescent current of 10mA is far too high and wastes battery life. Use a low-IQ PFM buck to achieve μA-level standby current.
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5V rail at 2.5A peak load: The 1A maximum output current rating is insufficient and risks permanent device damage from overcurrent and thermal runaway. Use a multi-phase buck controller to deliver higher continuous currents safely.
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High efficiency 12V → 5V conversion for thermal budget: Linear dropout of up to 1.4V at 1A causes excessive power dissipation and thermal stress. Use a high-current synchronous buck with external FETs to minimize losses and prevent overheating.
Application Notes
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The device has a single positive fixed 5V output; no external feedback components are needed, simplifying layout but limiting voltage flexibility.
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The package is SOT-89 (TO-243AA); ensure the PCB copper area connected to the tab is maximized for heat dissipation and connected to a proper thermal via network.
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The enable pin is internally connected to ground (no enable function); input voltage must be stable and rise monotonically to avoid unexpected startup behavior.
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Noise-sensitive circuits should keep input and output capacitors close to the device pins to minimize high-frequency noise coupling; use low-ESR ceramic capacitors (≥10µF recommended).
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No switching node (SW) exists since this is a linear device; however, careful routing to avoid coupling input noise onto output traces is essential for maintaining clean output voltage.
Gotchas
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[Ignoring dropout voltage at full load]: Engineers often assume the 5V output is regulated down to the input voltage minus a low dropout, but the 1.4V dropout at 1A means that input voltage below ~6.4V causes output to collapse below 5V. Symptom: output voltage drops under load, causing system brownout. Fix: Verify input voltage margin ≥ dropout + output voltage under worst-case load.
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[Inadequate thermal PCB design]: Relying on the small SOT-89 package pins alone for heat dissipation causes junction overheating despite staying under current limits. Symptom: device enters thermal shutdown or exhibits output voltage drift during continuous load. Fix: Use wide copper pours with thermal vias under the tab and measure junction temperature during prototype testing.
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[Low ESR capacitor assumption]: Using only electrolytic capacitors with high ESR on output can cause regulator instability or excessive output ripple. Symptom: oscillations visible on scope or intermittent output voltage glitches. Fix: Use ceramic capacitors with low ESR close to the output pin to maintain stability.
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[Startup with input voltage ramp slower than device response]: The device expects a stable input voltage; slow ramps near the dropout region can cause the output to oscillate or never reach full 5V output. Symptom: output voltage slowly ramps or fluctuates during power-up. Fix: Ensure input voltage ramps quickly above dropout voltage to guarantee stable startup behavior.