RT9166A-18GG Linear Voltage Regulator Equivalent & Substitute Parts

Part Overview

The RT9166A-18GG is an active linear voltage regulator IC manufactured by Richtek USA Inc., designed to deliver a fixed 1.8V output at up to 600mA in a surface-mount SOT-223 package. This device functions as a positive fixed output regulator with integrated over-current and over-temperature protection. The part is currently in active production status with substantial inventory availability (27,400 pcs). Equivalent and substitute parts are identified when component availability is constrained, supply chain disruptions occur, or design flexibility is required while maintaining electrical and mechanical compatibility within specified parameter tolerances.

Key Parameters

Parameter	Value
Manufacturer Part Number	RT9166A-18GG
Manufacturer	Richtek USA Inc.
Category	Power Management (PMIC)
Package / Case	TO-261-4, TO-261AA (SOT-223)
Output Configuration	Positive Fixed
Voltage - Output (Fixed)	1.8V
Current - Output (Max)	600mA
Voltage - Input (Max)	5.5V
Voltage Dropout (Max)	0.58V @ 600mA (Typ)
Operating Temperature Range	-40°C ~ 85°C
Mounting Type	Surface Mount
Product Status	Active
RoHS Status	ROHS3 Compliant

Substitute Part Grouping Explanation

Substitution eligibility for the RT9166A-18GG is determined by the following critical parameters:

Fixed Output Voltage: 1.8V (exact match required)
Output Current Capability: 600mA minimum
Package Type: SOT-223 (TO-261-4, TO-261AA) for mechanical and thermal compatibility
Output Configuration: Positive fixed output
Operating Temperature Range: -40°C ~ 85°C minimum
Regulatory Compliance: ROHS3 Compliant, REACH Unaffected

The AP2111H-1.8TRG1 qualifies as a direct substitute based on matching all critical parameters. Both devices deliver identical fixed 1.8V output, support 600mA load current, utilize the same SOT-223 package footprint, and operate across the required temperature range with equivalent regulatory compliance.

Parameter Comparison

Parameter	RT9166A-18GG (Main Part)	AP2111H-1.8TRG1 (Substitute)
Manufacturer	Richtek USA Inc.	Diodes Incorporated
Category	Power Management (PMIC)	Power Management (PMIC)
Package / Case	TO-261-4, TO-261AA (SOT-223)	TO-261-4, TO-261AA (SOT-223-3)
Output Configuration	Positive Fixed	Positive Fixed
Voltage - Output (Fixed)	1.8V	1.8V
Current - Output (Max)	600mA	600mA
Voltage - Input (Max)	5.5V	6V
Voltage Dropout (Max)	0.58V @ 600mA (Typ)	1.3V @ 600mA
Current - Quiescent (Iq)	300 µA	80 µA
PSRR	55dB (1kHz)	65dB (100Hz ~ 1kHz)
Protection Features	Over Current, Over Temperature	Over Current, Over Temperature, Under Voltage Lockout (UVLO)
Operating Temperature Range	-40°C ~ 85°C	-40°C ~ 85°C
Mounting Type	Surface Mount	Surface Mount
Product Status	Active	Active
RoHS Status	ROHS3 Compliant	ROHS3 Compliant
Moisture Sensitivity Level (MSL)	3 (168 Hours)	1 (Unlimited)

Engineering Selection Recommendations

Both the RT9166A-18GG and AP2111H-1.8TRG1 are active production devices with ROHS3 compliance and REACH unaffected status, qualifying them for equivalent use in applications requiring a fixed 1.8V, 600mA linear regulator in SOT-223 packaging.

The RT9166A-18GG exhibits lower dropout voltage (0.58V typical) and higher quiescent current (300 µA), making it suitable for applications with tighter input voltage margins or where dropout performance is critical.

The AP2111H-1.8TRG1 provides lower quiescent current (80 µA), higher PSRR (65dB), and includes Under Voltage Lockout (UVLO) protection, offering advantages in battery-powered or noise-sensitive applications. Its MSL rating of 1 (unlimited) provides superior moisture handling compared to the RT9166A-18GG MSL rating of 3 (168 hours).

Selection between these parts depends on specific application requirements regarding dropout voltage, quiescent current, noise rejection, and moisture sensitivity considerations.

Frequently Asked Questions (FAQ)

Q: Can the AP2111H-1.8TRG1 directly replace the RT9166A-18GG without PCB modifications?

A: Yes. Both devices use identical SOT-223 package pinouts (TO-261-4, TO-261AA) and deliver the same 1.8V fixed output at 600mA, enabling direct pin-compatible substitution without PCB layout changes.

Q: What are the key electrical differences between these two regulators?

A: The RT9166A-18GG features lower dropout voltage (0.58V typical vs. 1.3V), while the AP2111H-1.8TRG1 offers lower quiescent current (80 µA vs. 300 µA), higher PSRR (65dB vs. 55dB), and includes UVLO protection. Input voltage tolerance differs slightly (5.5V vs. 6V maximum).

Q: Which part is better for battery-powered applications?

A: The AP2111H-1.8TRG1 is more suitable for battery applications due to its significantly lower quiescent current (80 µA), which reduces standby power consumption and extends battery life.

Q: Are there any compliance or certification differences?

A: Both parts are ROHS3 compliant and REACH unaffected. The AP2111H-1.8TRG1 has a superior MSL rating of 1 (unlimited moisture exposure) compared to the RT9166A-18GG MSL rating of 3 (168 hours), providing better protection during storage and assembly processes.

Q: What is the maximum input voltage for each regulator?

A: The RT9166A-18GG supports maximum input voltage of 5.5V, while the AP2111H-1.8TRG1 supports 6V maximum input voltage. Both operate safely within their specified ranges.

Q: Can these parts be used interchangeably in all applications?

A: Interchangeability depends on application-specific requirements. Applications sensitive to dropout voltage, quiescent current, or noise performance may require evaluation of the specific electrical characteristics before substitution.

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