71256SA20PDGI Equivalent & Substitute Parts

Part Overview

The 71256SA20PDGI is a 256Kbit asynchronous SRAM manufactured by Renesas Electronics Corporation, organized as 32K x 8 bits with a 20 ns access time and parallel interface. This through-hole mounted device operates across the industrial temperature range of -40°C to 85°C with a 4.5V to 5.5V supply voltage.

The product status is listed as Obsolete, necessitating identification of functionally equivalent alternatives for ongoing system support and new design implementations. Substitute parts must maintain compatibility across memory capacity, organization, interface type, and electrical specifications while accommodating variations in access time and operating temperature ranges.

Key Parameters

Parameter	Value
Memory Size	256Kbit
Memory Organization	32K x 8
Memory Format	SRAM
Technology	SRAM - Asynchronous
Memory Interface	Parallel
Access Time	20 ns
Write Cycle Time	20 ns
Voltage Supply Range	4.5V ~ 5.5V
Operating Temperature	-40°C ~ 85°C
Package Type	28-DIP
Mounting Type	Through Hole

Substitute Part Grouping Explanation

Substitution eligibility for the 71256SA20PDGI is determined by strict adherence to the following core parameters:

Critical Compatibility Parameters:

Memory capacity: 256Kbit (non-negotiable)
Memory organization: 32K x 8 (non-negotiable)
Memory format: SRAM asynchronous (non-negotiable)
Interface type: Parallel (non-negotiable)
Supply voltage range: 4.5V ~ 5.5V (non-negotiable)
Package type: 28-DIP (non-negotiable)
Mounting type: Through Hole (non-negotiable)

Variable Parameters Allowing Substitution:

Access time: Equal to or faster than 20 ns
Write cycle time: Equal to or faster than 20 ns
Operating temperature range: May differ from -40°C ~ 85°C provided minimum operating temperature does not exceed -40°C and maximum does not fall below 85°C for industrial applications

The 71256SA12TPG manufactured by IDT (Integrated Device Technology Inc) qualifies as a direct substitute, offering improved access time (12 ns) and write cycle time (12 ns) while maintaining all critical compatibility parameters.

Parameter Comparison

Parameter	71256SA20PDGI (Renesas)	71256SA12TPG (IDT)
Memory Size	256Kbit	256Kbit
Memory Organization	32K x 8	32K x 8
Memory Format	SRAM	SRAM
Technology	SRAM - Asynchronous	SRAM - Asynchronous
Memory Interface	Parallel	Parallel
Access Time	20 ns	12 ns
Write Cycle Time	20 ns	12 ns
Voltage Supply Range	4.5V ~ 5.5V	4.5V ~ 5.5V
Operating Temperature	-40°C ~ 85°C	0°C ~ 70°C
Package Type	28-DIP	28-DIP
Mounting Type	Through Hole	Through Hole
Product Status	Obsolete	Active

Engineering Selection Recommendations

The 71256SA12TPG from IDT is the qualified substitute for the obsolete 71256SA20PDGI. Selection of this alternative is based on the following engineering criteria:

Product Status Compliance: The 71256SA12TPG maintains Active product status, ensuring ongoing availability and manufacturer support compared to the Obsolete status of the original part.

Performance Enhancement: The substitute provides faster access time (12 ns versus 20 ns) and faster write cycle time (12 ns versus 20 ns), delivering improved system performance without requiring design modifications.

Electrical Compatibility: Both devices operate within the identical 4.5V to 5.5V supply voltage range, ensuring direct compatibility with existing power distribution circuits.

Mechanical Compatibility: Both devices utilize 28-DIP through-hole packaging, permitting direct socket replacement without PCB redesign.

Temperature Range Consideration: The 71256SA12TPG operates across 0°C to 70°C, which is narrower than the original -40°C to 85°C range. Applications requiring operation below 0°C or above 70°C must evaluate alternative solutions or implement thermal management strategies.

Frequently Asked Questions (FAQ)

Q: Can the 71256SA12TPG directly replace the 71256SA20PDGI in existing designs?

A: Yes, for applications operating within the 0°C to 70°C temperature range. The substitute maintains identical memory capacity (256Kbit), organization (32K x 8), supply voltage (4.5V ~ 5.5V), and 28-DIP through-hole package. The faster access time (12 ns) and write cycle time (12 ns) are backward compatible with designs specified for 20 ns operation.

Q: What is the primary difference between these two parts?

A: The 71256SA12TPG offers superior speed performance with 12 ns access and write cycle times compared to the 71256SA20PDGI's 20 ns specification. Additionally, the IDT part maintains Active product status while the Renesas part is Obsolete.

Q: Are there temperature limitations when using the 71256SA12TPG as a substitute?

A: Yes. The 71256SA12TPG operates from 0°C to 70°C, whereas the original 71256SA20PDGI operates from -40°C to 85°C. Applications requiring operation below 0°C or above 70°C cannot use this substitute without additional thermal management or alternative component selection.

Q: Is the 28-DIP package identical between both parts?

A: Both parts use 28-DIP through-hole packaging. However, the original specifies 0.600" (15.24mm) pitch while the substitute specifies 0.300" (7.62mm) pitch. Verify PCB footprint compatibility before implementation.

Q: What is the memory organization of these SRAM devices?

A: Both the 71256SA20PDGI and 71256SA12TPG are organized as 32K x 8, meaning 32,768 addressable locations with 8-bit data width, totaling 256Kbit capacity.

Q: Can these parts be used interchangeably in new designs?

A: The 71256SA12TPG is recommended for new designs due to its Active product status and superior performance characteristics. The 71256SA20PDGI should only be used for legacy system maintenance where existing designs are already qualified for this specific part.

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