LP38843 - 3A Ultra-Low Dropout LDO with Enable | TI
MPN： LP38843 ✓ 啟用中LP38843 概覽
An ultra-low dropout (LDO) regulator is a type of linear voltage regulator that keeps its output stable even when the input voltage is only marginally higher than the output. Within the power management IC hierarchy, the LP38843 belongs to the low-dropout linear regulator class, positioned below DC-DC switching converters and commonly used as the final post-regulation stage for noise-sensitive rails.
Key features include up to 3A continuous output current, extremely low dropout voltage due to the N-MOS pass transistor architecture, stability with low-ESR ceramic output capacitors, and a separate Vbias input. The enable pin allows rail sequencing and low standby power in multi-rail systems. The fast transient response maintains regulation during load steps from zero to full 3A load, a critical parameter for DSP and FPGA core supplies.
Fabricated on a CMOS process, the LP38843 operates from two inputs: Vbias drives the gate of the N-MOS power transistor (typically from a 2.7V to 5.5V rail), while Vin supplies the load and can fall to very low levels because the low Vgs requirement minimizes headroom. This dual-supply topology yields dropout performance unachievable with PNP-based LDOs and drastically reduces ground current compared to bipolar designs.
Typical applications include DSP and processor core power supplies (1.2V/1.5V rails), point-of-load regulation on telecom and networking cards, and post-regulation of switching converter outputs where the LP38843 strips switching ripple before it reaches sensitive silicon.
Design consideration: Vbias must be present and above its UVLO before or with Vin; ensure the enable pin is actively driven rather than left floating, and size the PCB copper area under the TO-220-5 or TO-263 tab for thermal dissipation at full 3A load. Pricing as of 2026-08-30 per distributor listings.
直接替換替代品，適用於 LP38843 — 相同封裝，腳位對腳位相容。需重新設計 PCB 的不同封裝零件不列入。
LP38843T-1.2
✅ 直接替換📋 參考替代品（不在目錄中）
LP38843S-1.2/NOPB
✅ 直接替換📋 參考替代品（不在目錄中）
LP38842T-1.2
✅ 直接替換 ⚠️ 規格未經驗證📋 參考替代品（不在目錄中）
LP38852T-1.2
✅ 直接替換 ⚠️ 規格未經驗證📋 參考替代品（不在目錄中）
LT1965
⚡ 相同封裝 ⚠️ 規格未經驗證📋 參考替代品（不在目錄中）
LP38843 最大額定值與電氣特性
| 輸出類型 | Positive Fixed |
| Output Current | 3 A |
| Minimum Input Voltage (Vin) | 1.01 V |
| 壓降電壓 | Ultra-low dropout (N-MOS pass transistor) |
| 輸出數量 | 1 |
| 致能腳位 | Yes |
| Output Capacitor Stability | Stable with ceramic output capacitors |
| 封裝 | TO-220-5 (NDZ), TO-263 (KTT) |
| 安裝類型 | Through Hole (TO-220-5) / Surface Mount (TO-263) |
| Process Technology | CMOS with N-MOS power transistor |
| Fixed Output Options | 1.2 V, 1.5 V (order code dependent) |
LP38843 腳位配置
| 腳位 1 | VIN — Input voltage supply (down to 1.01V) |
| 腳位 2 | GND — Ground |
| 腳位 3 | EN — Enable input, actively drive - do not float |
| 腳位 4 | VBIAS — Bias supply to drive N-MOS gate (2.7V-5.5V typical) |
| 腳位 5 | VOUT — Regulated fixed output, connect ceramic output capacitor |
典型應用
LP38843 適用於 6 應用s: DSP Core Power Supply, Point-of-Load Regulation on Telecom Cards, Post-Regulation of Switching Converters, FPGA and Processor I/O Rails, Industrial Control and Automation Supplies, Test and Measurement Instrumentation.
DSP Core Power Supply
DSP cores such as TI C2000 series require tightly regulated 1.2V/1.5V rails with high current and fast transient response. The LP38843 delivers 3A from a minimum Vin of 1.01V, and its N-MOS CMOS topology provides an extremely low dropout so the rail stays in regulation even when the upstream 1.8V rail sags. The fast loop response handles zero-to-full-load steps without excessive undershoot, and the enable pin lets a sequencer stagger core and I/O rails, protecting the DSP from latch-up conditions during power-up.
推薦
Point-of-Load Regulation on Telecom Cards
Telecom and networking line cards distribute a mid-rail bus and generate low-voltage local rails for ASICs and PHYs. The LP38843 fits as a point-of-load 3A LDO where headroom is small: Vin can fall to 1.01V while Vbias rides a higher 2.7V-5.5V aux rail to drive the N-MOS gate. This dual-supply arrangement wastes minimal power in dropout and, unlike a second buck stage, adds no switching noise near sensitive receive circuitry, simplifying EMI design on dense cards.
推薦
Post-Regulation of Switching Converters
After a buck converter, residual switching ripple in the 100 kHz-MHz range can degrade ADC and PLL noise floors. The LP38843 placed as a post-regulator strips this ripple with its high PSRR and low noise while supplying up to 3A. It is stable with inexpensive ceramic output capacitors, keeping the post-regulation stage compact and low-cost. Design the dropout budget so the buck output sits only 200-400mV above the LDO output to limit power dissipation at full load.
推薦
FPGA and Processor I/O Rails
FPGA I/O banks commonly need fixed 1.5V rails at 1-3A with tight DC accuracy. The LP38843 fixed-output versions (1.2V, 1.5V) simplify the BOM with no feedback divider, and the enable pin supports power sequencing between VCCIO and VCCINT rails required by FPGA vendors. Because the part is stable with ceramic capacitors, multiple LP38843 channels can be placed close to FPGA banks, minimizing trace inductance and improving transient behavior during simultaneous switching outputs.
推薦
Industrial Control and Automation Supplies
Industrial controllers require rugged point-of-load regulation tolerant of supply variation. The LP38843 operates from a minimum Vin of 1.01V and survives low-line conditions during brownouts, keeping logic rails alive. The enable pin supports controlled shutdown for safety sequencing, and the TO-220-5 package simplifies thermal design with its tab connected to ground for heatsinking. Ceramic-capacitor stability also improves long-term reliability by avoiding electrolytic capacitors in high-vibration environments.
推薦
Test and Measurement Instrumentation
Bench instruments and ATE boards need clean, high-current local rails with predictable behavior. The LP38843's CMOS N-MOS architecture yields low ground current and low dropout, so calibration drifts from self-heating are minimized. Its fast transient response makes it suitable for feeding clock distribution and ADC reference buffers that see dynamic loads. In TO-263 (KTT) surface mount, it integrates into automated assembly, and the enable pin allows per-board rail bring-up under software control during self-test.
推薦
推薦產品摘要
工程參考資料，適用於 LP38843 — 比較、設計指引及合規資訊。
選型指南
與替代品比較
| 參數 | 本產品 | LP38843T-1.2 | LP38843S-1.2/NOPB | LP38842T-1.2 | LT1965 |
|---|---|---|---|---|---|
| Package | TO-220-5 (NDZ) / TO-263 (KTT) | TO-220-5 (NDZ) - same | TO-263 (KTT) - same family | TO-220-5 (NDZ) - same | TO-220-5 - same package, different pinout |
| Brand | Texas Instruments | Texas Instruments | Texas Instruments | Texas Instruments | Analog Devices |
| Output Current | 3 A | 3 A | 3 A | 3 A | 1.5 A |
| Dual Supply (Vin + Vbias) | Yes | Yes | Yes | Yes | No (single supply) |
主要差異化特點
- Enable pin for rail sequencing (對比LP38842T-1.2)
- Higher 3A output current (對比LT1965)
- Extremely low minimum Vin of 1.01V (對比LP38843S-1.2/NOPB)
設計說明
The LP38843 requires Vbias to be present and above its UVLO before or simultaneously with Vin, since Vbias drives the N-MOS pass transistor gate. If Vbias comes up late, the output will not regulate even with Vin present. In sequenced systems, use the EN pin with a supervisor to guarantee correct ordering, and never leave EN floating - drive it actively from logic or a pull-up.
At 3A output, power dissipation equals (Vin - Vout) x 3A plus bias power. For example, dropping 1.8V to 1.2V at 3A dissipates 1.8W. The TO-220-5 tab (at ground potential) should be mounted to a heatsink or a generous copper pour; for TO-263, use at least 1 square inch of PCB copper on the thermal plane. Verify junction temperature stays within datasheet limits at worst-case ambient.
Place a ceramic output capacitor close to the VOUT pin; the device is stable with ceramics, but keep trace inductance low for good transient response. Input capacitance on both VIN and VBIAS should also sit near their pins. Keep the high-current VIN-to-VOUT path wide and short, and route EN away from the power loop to avoid glitching during load transients.
合規資訊
NOPB suffix on TI order codes denotes No Pb (lead-free) plating; verify full RoHS/REACH status on TI product page.
