Complete NJM7905FATEG Datasheet: Specs & Electrical Tables
Key Takeaways (Quick Insights)
- Stable -5V Output: Guaranteed precision for sensitive analog signal chains.
- 60dB PSRR: Effectively filters ripple to improve Op-Amp SNR.
- Thermal Ruggedness: Integrated short-circuit and thermal overload protection.
- 200mA Capability: Provides 2x the headroom of standard 79Lxx series regulators.
Precise regulator specifications determine headroom and thermal margins for negative rails; for many mixed-signal designs, a 100–200 mV margin can be the difference between stable operation and oscillation. This guide transforms raw datasheet parameters into actionable engineering insights.
Background & Quick Overview
Device Application & Utility
Point: This device is a three-terminal negative fixed regulator. Evidence: Manufacturer documentation lists a nominal output of −5 V with a specified maximum output current in the low hundreds of milliamps. Explanation: Designers enlist this regulator for low-voltage negative rails where board-level simplicity and modest current are required, such as biasing op amps, reference rails, and small analog blocks.
Competitive Differentiation
| Metric | NJM7905FATEG | Generic 79L05 | Advantage |
|---|---|---|---|
| Output Current | Up to 200mA | 100mA | Higher dynamic load support |
| Ripple Rejection | 60 dB (typ) | 45-50 dB | Cleaner analog rails |
| Quiescent Current | 8 mA (Stable) | 6-10 mA (Variable) | Predictable thermal idling |
Pinout & Absolute Maximum Ratings
Pin 1: INPUT (Negative Supply)
Pin 2: GROUND (Reference)
Pin 3: OUTPUT (-5V Fixed)
Tab: Case/Thermal (Connected to GND for better shielding)
Core Electrical Characteristics
| Parameter | Symbol | Typ. Value | Units |
|---|---|---|---|
| Output Voltage | VOUT | -5.0 | V |
| Line Regulation | ΔV/ΔVin | 2 | mV |
| Dropout Voltage | VDO | 1.5 | V |
"When deploying the NJM7905FATEG in high-precision audio circuits, the most common pitfall is ignoring the output capacitor's ESR. While modern MLCCs are tempting, a 10µF Tantalum or a low-ESR Electrolytic often provides the phase margin needed to prevent -5V rail oscillation during transient steps. Also, remember that since this is a negative regulator, the 'Input' voltage is more negative than the 'Output' (e.g., -10V in, -5V out)."
* Hand-drawn schematic, not an exact circuit diagram.
Layout Pro-Tip:
- Kelvin Sensing: Connect the ground pin directly to the load's star ground to avoid IR-drop errors.
- Thermal Vias: Place at least 4-6 vias (0.3mm) under the TO-252 tab to the bottom copper layer.
Summary & Integration Checklist
- Voltage Margin: Maintain at least -2.0V difference between Input and Output for worst-case regulation.
- Capacitor Selection: Use 0.1µF Ceramic on Input and 10µF+ on Output for stability.
- Thermal Calculation: Power (W) = (|Vin| - |Vout|) × Iout. Ensure TJ
- BOM Check: Verify FATEG suffix for TO-252 (DPAK) surface mount variant.
