HM5225405B 256-Mbit SDRAM Technical Summary

Overview

The Hitachi HM5225405B is a high-performance 256-Mbit Synchronous DRAM (SDRAM) organized as 16,777,216 words × 4-bit × 4 banks. This component is part of Hitachi's family of 256-Mbit SDRAM devices that includes variations with different word/bit configurations. The HM5225405B is designed for applications requiring high-speed memory access with low power consumption, operating with a 3.3V power supply and featuring LVTTL interfaces for compatibility with modern digital systems.

All operations are synchronized to the rising edge of the clock input, providing precise timing control. The device is packaged in a space-efficient 54-pin plastic TSOP II package, making it suitable for applications where board space is at a premium.

Key Features

• Memory Organization: 16,777,216 words × 4-bit × 4 banks (256 Mbit)
• Power Supply: 3.3V ±0.3V
• Clock Frequency: Up to 133 MHz (75 ns) or 100 MHz (100 ns) operation
• Interface: LVTTL compatible inputs and outputs
• Bank Architecture: 4 independent banks supporting concurrent operations
• Burst Operation: Programmable burst lengths (1, 2, 4, 8) with sequential or interleave sequencing
• CAS Latency: Programmable (2 or 3 clock cycles)
• Refresh: 8192 refresh cycles every 64ms with auto refresh and self refresh modes
• Data Control: Byte control via DQM (Data Input/Output Mask)
• Package: 54-pin plastic TSOP II (10.16mm × 22.22mm)

Applications

The HM5225405B is designed for use in a wide range of electronic systems requiring high-density, high-speed memory:

• Computer systems and peripherals
• Networking equipment (routers, switches)
• Telecommunications infrastructure
• Consumer electronics (digital TVs, set-top boxes)
• Industrial control systems
• Embedded systems
• Graphics subsystems
• Test and measurement equipment

Electrical Characteristics

Absolute Maximum Ratings

• Supply Voltage (VDD/VDDQ): -0.5V to +4.6V
• Input Voltage (VI): -0.5V to VDDQ +0.5V
• Output Voltage (VO): -0.5V to VDDQ +0.5V
• Operating Temperature: 0°C to +70°C (commercial)
• Storage Temperature: -55°C to +150°C

Recommended Operating Conditions

• Supply Voltage (VDD/VDDQ): 3.3V ±0.3V
• Input High Voltage (VIH): 2.0V min (VDDQ = 3.0V)
• Input Low Voltage (VIL): 0.8V max (VDDQ = 3.0V)
• Operating Temperature: 0°C to +70°C

DC Characteristics

• Input Leakage Current (II): ±1 μA max
• Output Leakage Current (IOZ): ±1 μA max
• Operating Current (IDD): 120 mA max (133 MHz operation)
• Standby Current (ISB): 20 mA max (LVTTL inputs)
• Self Refresh Current (ISR): 2 mA max

AC Characteristics

• Clock Cycle Time (tCK): 7.5 ns min (133 MHz), 10 ns min (100 MHz)
• CAS Latency: 2 or 3 clock cycles (programmable)
• Access Time (tAC): 5.4 ns max (133 MHz)
• Address Setup Time (tAS): 1.5 ns min
• Address Hold Time (tAH): 0.8 ns min
• Data-in Setup Time (tDS): 1.5 ns min
• Data-in Hold Time (tDH): 0.8 ns min

Functional Description

Memory Architecture

The HM5225405B is organized as four independent memory banks, each containing 16,777,216 addressable locations of 4 bits each. This architecture allows simultaneous activation of different banks, significantly improving memory access efficiency compared to single-bank designs.

Burst Operation

The device supports programmable burst lengths of 1, 2, 4, or 8 with two sequencing options:

• Sequential: Linear address incrementing
• Interleave: Address sequencing according to a predefined interleave pattern

Refresh Modes

The HM5225405B provides two refresh modes to maintain data integrity:

• Auto Refresh: Requires external refresh control at 8192 cycles every 64ms
• Self Refresh: Internal timer maintains refresh automatically during low-power states

Package Information

54-pin TSOP II Package Details

• Package Type: Plastic Thin Small Outline Package (TSOP) Type II
• Package Dimensions: 10.16mm × 22.22mm body size
• Lead Pitch: 0.8mm
• Lead Count: 54 pins
• Lead Material: Alloy 42 or copper alloy
• Package Weight: Approximately 0.23g

Pin Configuration

The 54-pin TSOP II package includes the following signal groups:

• Clock and clock enable (CLK, CKE)
• Bank address inputs (BA0, BA1)
• Address inputs (A0-A11)
• Data inputs/outputs (DQ0-DQ3)
• Data mask (DQM)
• Control signals (CS, RAS, CAS, WE)
• Power and ground (VDD, VDDQ, VSS, VSSQ)

Ordering Information

The device is available in different speed grades and temperature ranges:

• HM5225405B-75: 133 MHz operation (7.5ns cycle time)
• HM5225405B-A6: 100 MHz operation (10ns cycle time)
• HM5225405B-B6: Extended temperature range variant

Conclusion

The Hitachi HM5225405B 256-Mbit SDRAM provides a high-performance memory solution for applications requiring fast access times and high density in a compact package. With