The **ADP7158ACPZ-2.8-R7** is a high-performance, ultra-low noise, high Power Supply Rejection Ratio (PSRR) linear regulator (LDO) manufactured by Analog Devices. It is specifically designed to provide clean power to noise-sensitive precision analog circuits. --- ### 1. Key Technical Specifications | Parameter | Specification | |:---|:---| | **Output Voltage (Fixed)** | 2.8 V | | **Input Voltage Range** | 2.3 V to 5.5 V | | **Maximum Output Current** | 2 A | | **Typical Noise** | 0.9 µV rms (100 Hz to 100 kHz) | | **PSRR** | >60 dB at 1 MHz; 70 dB at 10 kHz | | **Dropout Voltage** | 120 mV (typical) at 2 A load | | **Package** | 10-lead LFCSP (3mm x 3mm) | | **Operating Temperature** | -40°C to +125°C | --- ### 2. Core Functional Parts & Pins The device architecture is optimized for stability and noise suppression. Below are the critical pin functions: * **VIN (Input Supply):** The power source for the LDO. It requires a decoupling capacitor to ground to minimize input ripples. * **VOUT (Regulated Output):** Delivers the stable 2.8V. A low ESR ceramic capacitor is required for stability. * **EN (Enable):** A logic-level input. Driving this high turns on the device; driving it low puts it into a low-current shutdown mode. * **VREG (Internal Regulator):** An internal supply for the control circuitry. It usually requires an external bypass capacitor. * **REF (Reference):** Connections for an external capacitor to filter the internal voltage reference, which is the key to achieving the sub-1µV noise performance. * **BYP (Bypass):** Used to further filter noise from the error amplifier. * **Exposed Pad:** Essential for thermal management; it must be soldered to the PCB ground plane to dissipate heat generated during high current output. --- ### 3. Key Advantages #### A. Ultra-Low Noise With a noise floor of roughly **0.9 µV rms**, this LDO is one of the cleanest in the industry. This is vital for powering High-Speed ADCs, DACs, and precision VCOs where power supply noise directly translates to jitter or signal degradation. #### B. High PSRR Its ability to reject power supply noise (over 60dB at high frequencies like 1MHz) makes it ideal for post-regulating switching power supplies. It "cleans up" the high-frequency ripples left behind by DC-DC converters. #### C. High Current Capability While most low-noise LDOs are limited to 100mA - 500mA, the ADP7158 provides up to **2 Amperes**, allowing it to power entire RF signal chains or large FPGAs. --- ### 4. Typical Application Circuit ```text [Input 3.3V] ----+----[ VIN ] [ VOUT ]----+---- [Output 2.8V] | | [Cin] [Cout] | | [GND]-----------------------[GND] ``` * **Cin:** Typically 10 µF Ceramic. * **Cout:** Typically 10 µF Ceramic (low ESR). * **Cref/Cbyp:** Specific small-value capacitors (e.g., 1µF) are added to the REF and BYP pins to achieve the datasheet noise specs.