• Created:2026/01/22
• Updated:2026/01/22
• Author:
  Takeshi Takatsudo

L7805ABD2T-TR - +5V Linear Regulator

Fixed positive voltage regulator providing stable +5V output in compact TO-263-2 (D2PAK) surface-mount package with excellent thermal performance.

• 🔗 View on JLCPCB: C86206
• 📄 Download Datasheet (PDF)

Overview

The L7805ABD2T-TR is a three-terminal positive voltage regulator in TO-263-2 (D2PAK) package, designed to provide a fixed +5V output from a higher input voltage. This component serves as the final stage in the +5V power rail, converting the +7.5V DC-DC output to a clean, low-noise +5V suitable for modular synthesizer digital circuits and control voltage applications.

Key Specifications

Parameter	Value	Notes
JLCPCB Part Number	C86206
Manufacturer Part Number	L7805ABD2T-TR
Package	TO-263-2 (D2PAK)	Surface-mount
Stock Availability	272,379 units	Very high availability
Unit Price	$0.11	JLCPCB pricing
Output Voltage	5V ±4%	4.8V - 5.2V
Output Current	1.5A max	Design uses 0.5A
Dropout Voltage	~2V typical	Minimum VIN = 7V
Line Regulation	±0.5% typical	Input voltage variation
Load Regulation	±1% typical	Output current variation
Ripple Rejection	>60dB	@120Hz
Quiescent Current	~5mA typical	No-load consumption
Thermal Resistance θJC	3°C/W	Junction to case (tab)
Thermal Resistance θJA	35°C/W	Junction to ambient
Operating Temp Range	0°C to +125°C	Junction temperature

Pin Configuration

         TO-263-2 (D2PAK) Package
              Top View

         ┌──────────────┐
         │              │
         │   L7805A     │
         │   BD2T-TR    │
         │              │
         │              │
         └──┬───────┬───┘
            │       │
          PIN1    PIN2
          INPUT    GND
         (+7.5V) (Common)

              TAB
           (OUTPUT)
            (+5V)


         Side View

         ┌──────────────┐
         │   Component  │ ← Surface mount IC
         └──┬───────┬───┘
            │       │
          PIN1    PIN2

    ════════════════════  ← Metal tab (OUTPUT)
                            soldered to PCB pad

Pin Descriptions

Pin	Name	Function	Connection in Design
1	INPUT	Unregulated input voltage	+7.5V from DC-DC converter (U3)
2	GND	Ground reference (common)	System ground plane
TAB	OUTPUT	Regulated +5V output (metal tab)	+5V rail with protection circuit

Note: Unlike TO-220 package, the TO-263-2 has the OUTPUT on the metal tab, not on pin 3.

Application Circuit

+7.5V (from DC-DC) ───┬─── C12: 470nF ───┬─── U7: L7805ABD2T ───┬─── C15: 100nF ───┬─→ +5V OUT
                      │                  │                      │                  │
                      │                  │    ┌──────────┐      │                  │
                      │                  └────│1  INPUT  │      │                  │
                      │                       │          │      │                  │
                      │                    ┌──│2   GND   │      │                  │
                      │                    │  │          │      │                  │
                      │                    │  │   TAB ───┴──────┴──────────────────┤
                      │                    │  └──────────┘                         │
                      │                    │     (OUTPUT)                          │
                      └─── C19: 470µF ─────┼─────────┬─── C20: 470µF ──────────────┤
                           (Input)         │         │    (Output)                 │
                                           │         │                             │
                                          GND       GND                            │
                                                                                   │
                                        ┌──────────────────────────────────────────┘
                                        │
                                  ┌─────┴─────┐
                                  │   LED3    │ Blue Status LED
                                  │  (Blue)   │ via R8: 1kΩ
                                  └─────┬─────┘
                                        │
                                       GND

Component Values

Input Capacitors

Reference	Value	Type	Voltage	Package	Part Number	Purpose
C12	470nF	Ceramic X7R	25V	0603	C1623	High-frequency noise filtering
C19	470µF	Electrolytic	10V	D6.3xL7.7mm	C335982	Input voltage stabilization

Output Capacitors

Reference	Value	Type	Voltage	Package	Part Number	Purpose
C15	100nF	Ceramic X7R	50V	0805	C49678	High-frequency decoupling
C20	470µF	Electrolytic	10V	D6.3xL7.7mm	C335982	Load transient response

Status LED Circuit

Reference	Part	Value	Package	Part Number	Purpose
LED3	Blue LED	2.8V @ 10mA	0805	C72041	Power status indicator
R8	Resistor	1kΩ	0603	C21190	LED current limiting

Design Considerations

Input Voltage Requirements

The L7805ABD2T requires a minimum input voltage of approximately 7V for proper regulation (5V output + 2V dropout). In this design:

• Input voltage: +7.5V from LM2596S DC-DC converter
• Dropout margin: 7.5V - 5V = 2.5V
• Status: ✅ Excellent - well above minimum dropout voltage

The 2.5V margin provides:

1. Stable regulation across load variations
2. Tolerance for input voltage ripple
3. Reduced power dissipation compared to higher input voltages
4. Optimal efficiency for the linear regulator stage

Thermal Management

Power dissipation calculation:

P = (VIN - VOUT) × IOUT
P = (7.5V - 5V) × 0.5A
P = 2.5V × 0.5A
P = 1.25W

Temperature rise without additional heatsinking:

ΔT = P × θJA
ΔT = 1.25W × 35°C/W
ΔT = 43.75°C

At 25°C ambient, junction temperature = 68.75°C (well within 125°C maximum).

Thermal performance advantages of TO-263-2:

• Lower θJA than TO-220 (35°C/W vs 50°C/W)
• Large metal tab provides excellent heat spreading
• Direct thermal contact with PCB copper pour
• No additional heatsink required for this application

PCB copper area recommendations:

• Minimum: 2 cm² copper pour connected to tab
• Recommended: 5 cm² copper pour for better margin
• Thermal vias: 6-10 vias (0.3mm) under tab to bottom layer

Capacitor Placement

Critical for stability and noise rejection:

1. C12 (470nF ceramic): Place within 5mm of pin 1

   • Purpose: Suppress high-frequency noise from DC-DC stage
   • Type: X7R or better (maintains capacitance vs. temperature)

2. C19 (470µF electrolytic): Place within 10mm of pin 1

   • Purpose: Stabilize input voltage during load transients
   • Polarity: Positive terminal to input, negative to ground

3. C15 (100nF ceramic): Place within 5mm of output tab

   • Purpose: High-frequency output decoupling
   • Critical for preventing oscillation
   • Must be ceramic for low ESR/ESL

4. C20 (470µF electrolytic): Place within 10mm of output tab

   • Purpose: Improve load transient response
   • ESR: <2Ω for best performance
   • Helps with sudden current demands

Ground Plane Connection

The TO-263-2 package requires careful PCB layout:

• Pin 2 (GND): Connect directly to ground plane with wide trace
• Tab (OUTPUT): Large copper pour for both electrical and thermal connection
• Thermal vias: Essential for heat dissipation to inner/bottom layers
• Keep-out area: Maintain clearance around pins for solder inspection

Performance Characteristics

Regulation Performance

Condition	Specification	Typical Performance
Line regulation	VIN = 7V to 25V	±0.5% (±25mV)
Load regulation	IOUT = 5mA to 1.5A	±1% (±50mV)
Output voltage accuracy	At 25°C	±4% (±200mV)
Temperature coefficient	-40°C to +125°C	±1mV/°C typical

Noise Performance

Parameter	Value	Conditions
Ripple rejection	60dB min	f = 120Hz
Output noise voltage	<1mVp-p	With recommended capacitors
Transient response	<50µs	250mA load step
PSRR (Power Supply Rejection)	>60dB	100Hz - 10kHz

Protection Features

Built-in Protections

1. Thermal Shutdown: Automatically shuts down if junction temperature exceeds 150°C
2. Short Circuit Protection: Current limiting prevents damage during output short
3. Safe Operating Area (SOA): Internal circuitry ensures operation within safe limits
4. Reverse Polarity: Input diode protects against reverse voltage

External Protection (This Design)

+5V (from U7) ───┬─── PTC2: 1.1A ───┬─── F2: 1.5A ──┬─── TVS2: SD05 ────────┬─→ +5V OUT
                 │  (Auto-Reset)    │   (Backup)    │   (5V Clamp)          │
                 │                  │               │      ↕                │
                 │                  │               └─────GND────────────────┤
                 │                  │                                       │
                 └─── LED3 (Blue) via R8 (1kΩ) ──────────────→ Power Status

Protection stages:

1. Overload (0.6A-1.5A): PTC2 trips → Auto-reset after cooling
2. Short circuit (>1.5A): F2 blows → Manual replacement required
3. Overvoltage: TVS2 clamps transients above 6V (unidirectional)

Note: The TVS2 (SD05) is unidirectional, optimized for positive DC power rail protection.

Bill of Materials

Designator	Part	Value	Package	JLCPCB Part #	Qty	Unit Price	Extended
U7	L7805ABD2T-TR	Fixed +5V LDO	TO-263-2	C86206	1	$0.11	$0.11
C12	Ceramic Cap	470nF 25V X7R	0603	C1623	1	$0.0036	$0.0036
C15	Ceramic Cap	100nF 50V X7R	0805	C49678	1	$0.0021	$0.0021
C19, C20	Electrolytic	470µF 10V	D6.3xL7.7mm	C335982	2	$0.014	$0.028
LED3	LED	Blue 0805	0805	C72041	1	$0.0126	$0.0126
R8	Resistor	1kΩ ±1%	0603	C21190	1	$0.0005	$0.0005
				Total			$0.16

Alternative Parts

Direct Replacements (TO-263-2 Package)

Part Number	Manufacturer	JLCPCB Part #	Stock	Price	Notes
L7805ABD2T-TR	STMicroelectronics	C86206	272,379	$0.11	Recommended (very high stock)
MC7805BD2T	ON Semiconductor	Check	Check	~$0.12	Pin-compatible
UA7805CKC	Texas Instruments	Check	Check	~$0.13	Pin-compatible

Package Alternatives

Package	Part Number	JLCPCB Part #	Stock	Price	Notes
TO-263-2	L7805ABD2T-TR	C86206	272,379	$0.11	Recommended (best thermal)
TO-220	L7805CV	C2846	55,629	$0.11	Through-hole alternative
SOT-89	AMS1117-5.0	C6187	High	$0.05	Lower current (1A max)

Recommendation: Stick with TO-263-2 for SMD assembly and superior thermal performance.

PCB Layout Guidelines

Footprint Requirements

TO-263-2 (D2PAK) package footprint specifications:

         Top View (PCB Pad Layout)

    ┌──────────────────────────────┐
    │                              │
    │    Large Copper Pour         │  ← OUTPUT TAB
    │    (5cm² recommended)        │     thermal + electrical
    │                              │
    │         Thermal Vias         │
    │         (6-10 vias)          │
    │                              │
    └──────────────────────────────┘

         PIN1 ■        PIN2 ■
        (INPUT)        (GND)

    Pin spacing: 2.54mm (0.1")
    Pin pad: 1.5mm x 2.0mm
    Tab pad: 10mm x 10mm (minimum)
            15mm x 15mm (recommended)

Recommended Pad Dimensions

Pad	Width	Length	Purpose
Pin 1 (INPUT)	1.5mm	2.0mm	Solder pad for input pin
Pin 2 (GND)	2.0mm	3.0mm	Larger for ground connection
Tab (OUTPUT)	10-15mm	10-15mm	Thermal and electrical connection

Layout Recommendations

1. Component placement:

   • Orient IC with tab facing interior of PCB (away from edge)
   • Maximize copper area under and around tab
   • Keep input and output capacitors on same side as regulator

2. Copper pours:

   • Create large copper pour (5cm² minimum) connected to output tab
   • Top layer: Main output pad and distribution
   • Bottom layer: Additional copper connected via thermal vias
   • Inner layers (4-layer board): Additional ground/power planes

3. Thermal vias:

   • Place 6-10 thermal vias (0.3mm diameter) under tab
   • Arrange in grid pattern for even heat distribution
   • Connect to bottom layer copper pour
   • Do NOT use thermal relief on these vias (direct connection needed)
   • Via spacing: ~2mm apart

4. Trace widths:

   • Input trace (7.5V): 0.5mm minimum (0.5A current, low voltage drop)
   • Output trace (5V): 1mm minimum (0.5A current)
   • Ground: Maximum copper pour area
   • High-current paths: 2mm or copper pour preferred

5. Capacitor placement:

   C12 ──┐  ┌── IC ──┐  ┌── C15
         │  │        │  │
   C19 ──┘  │  U7    │  └── C20
            │        │
            └────────┘
   
   Distance:
   - C12: <5mm from pin 1
   - C19: <10mm from pin 1
   - C15: <5mm from output tab
   - C20: <10mm from output tab

Thermal Via Pattern

    Recommended thermal via pattern
    under TO-263-2 tab:

    ┌─────────────────────────┐
    │  ●    ●    ●    ●    ●  │
    │                         │
    │  ●    ●    ●    ●    ●  │  ← 0.3mm vias
    │                         │     2mm spacing
    │  ●    ●    ●    ●    ●  │
    │                         │
    └─────────────────────────┘

    Total vias: 15 (aggressive cooling)
    Minimum: 6 vias
    Recommended: 10 vias

Assembly Considerations

Soldering Guidelines

Reflow soldering (recommended for production):

• Peak temperature: 260°C maximum
• Time above 220°C: 60-90 seconds
• Solder paste: SAC305 or similar lead-free
• Stencil thickness: 0.125mm (5 mil)

Hand soldering:

• Soldering iron: 350°C maximum
• Solder pin 1 and pin 2 first
• Apply solder to tab from component side
• Ensure good thermal contact between tab and PCB pad
• Use generous solder for tab connection

Inspection Points

After assembly, inspect:

1. Pin solder joints: Smooth fillet, no bridges
2. Tab solder joint: Good coverage, no voids visible
3. Component alignment: Centered on pads
4. No cold solder joints: Shiny, smooth finish
5. Thermal via filling: Solder should wick into vias

Testing and Validation

Input Voltage Test

1. Apply 7.5V to input with no load
2. Verify output voltage: 4.8V - 5.2V (5V ±4%)
3. Measure quiescent current: <10mA

Load Regulation Test

1. Connect variable load (0-1.0A)
2. Measure output voltage at different load currents:
   • 0mA: Should be within 5V ±2%
   • 250mA: Should be within 5V ±3%
   • 500mA: Should be within 5V ±4%
3. Verify voltage drop <50mV from no-load to full-load

Thermal Test

1. Apply 0.5A load for 30 minutes
2. Measure case temperature with thermal camera or thermocouple
3. Verify case temperature <70°C at 25°C ambient
4. Compare to calculation: Should be ~69°C
5. Check for thermal shutdown (should not occur)

Ripple and Noise Test

1. Connect oscilloscope (AC coupling, 20MHz bandwidth limit)
2. Use short ground lead or coax probe
3. Measure output with 0.5A load
4. Verify peak-to-peak ripple <5mVp-p (target: <1mVp-p)
5. Check for oscillation or instability (should be stable)

Transient Response Test

1. Use electronic load with step function (0A → 0.5A)
2. Monitor output voltage on oscilloscope
3. Verify voltage dip <250mV during load step
4. Verify recovery time <100µs
5. Check for ringing or overshoot

Troubleshooting

Symptom	Possible Cause	Solution
No output voltage	Input voltage too low	Verify 7.5V input from DC-DC
	Shorted output	Check for shorts on +5V rail
	Thermal shutdown	Reduce load, check thermal vias
	Poor tab solder joint	Reflow tab solder connection
Low output voltage	Insufficient input voltage	Check DC-DC stage output (should be 7.5V)
	Excessive load current	Verify load <0.5A (design spec)
	Poor ground connection	Check pin 2 and ground plane
	High trace resistance	Check trace widths and connections
High ripple noise	Missing input capacitor	Verify C12, C19 installed correctly
	Missing output capacitor	Verify C15, C20 installed correctly
	Poor capacitor placement	Move capacitors closer to IC
	Ground loop issues	Check ground plane continuity
Oscillation	Missing C15 (100nF output)	Add C15 close to output tab
	Long output traces	Shorten traces, add local decoupling
	Capacitive load	Add series resistance (1Ω) at output
	Poor ground routing	Improve ground plane connections
Overheating	Excessive power dissipation	Check input voltage (should be 7.5V)
	Insufficient copper area	Increase copper pour under tab
	No thermal vias	Add thermal vias under tab
	Poor thermal contact	Check solder joint on tab
Voltage too high	Wrong regulator installed	Verify L7805A not L7812 or other
	Open feedback loop	Check internal IC (unlikely)
Voltage too low	Input voltage marginal	Verify 7.5V input stable
	Excessive load	Reduce load current

Application Notes

Digital vs. Analog Loads

The +5V rail in modular synthesizers may power:

Digital circuits (microcontrollers, logic ICs):

• Characteristics: Switching loads, transient currents
• Decoupling: Add 100nF ceramic capacitor at each IC
• Distribution: Star topology from main filter cap

Analog circuits (op-amps, comparators):

• Characteristics: Steady loads, noise-sensitive
• Decoupling: 100nF ceramic + 10µF electrolytic per section
• Isolation: Consider RC filter if needed (10Ω + 100µF)

Low-Noise Operation

For ultra-low-noise applications:

1. Additional output filtering:

   • Add 10Ω resistor + 100µF capacitor LC filter
   • Creates additional pole at ~160Hz
   • Reduces high-frequency noise

2. Separate analog/digital grounds:

   • Split +5V distribution into analog and digital sections
   • Join grounds at single star point
   • Prevents digital switching noise coupling

3. Shielding:

   • Route +5V traces away from high-frequency signals
   • Use ground plane as shield
   • Keep sensitive analog circuits away from digital sections

Related Components

• Upstream: LM2596S-ADJ #2 (U3) - Provides +7.5V input
• Downstream: Protection circuit (PTC2, F2, TVS2)
• Parallel regulators: L7812CV-DG (U6), CJ7912 (U8)

References

• L7805ABD2T-TR Datasheet - STMicroelectronics
• JLCPCB Part C86206
• TO-263 Package Thermal Design
• Related documentation: Diagram6 - +5V Linear Regulator