Fixed 1.8V rail for analog and logic supplies
The LD1117ADT18TR is a fixed 1.8V output LDO from STMicroelectronics, rated for 1A continuous output current. The 80dB PSRR at 120Hz makes it a strong candidate for post-regulating a switching pre-regulator feeding noise-sensitive analog or mixed-signal loads — think ADC reference supplies, PLL rails, or sensor front-ends where ripple rejection matters. Output is fixed at 1.8V, so no external feedback divider is needed. That saves two resistors and eliminates a noise-injection path on the sense node. For a 1.8V logic rail powering an MCU or small FPGA bank, the fixed output keeps the BOM simple.
Dropout headroom and thermal budget at 1A
Maximum dropout voltage is 1.3V at 1A. That means the input must stay above 3.1V to maintain regulation at full load. If your rail is a nominal 3.3V with ±5% tolerance, the worst-case input dips to 3.135V — that leaves only 35mV of headroom above the dropout ceiling. In that scenario, either raise the input rail or reduce the load current. The 10 mA quiescent current is typical for a 1A LDO of this generation; it adds about 18 mW of dissipation at 1.8V out, negligible compared to the pass-element loss. At 1A with 1.3V dropout, the pass-element dissipates 1.3W. Without adequate copper area, junction temperature will exceed the 125°C maximum at ambient above 70°C. A 2-oz copper pour of at least 500 mm² on the tab side keeps the junction within limits.
For volume pricing and lead time, submit an RFQ against your BOM quantity. The LD1117 family has broad second-source coverage from multiple manufacturers, so supply risk is low. We source per order — confirm the required quantity and target delivery window at quote time.