M27W256 STMICROELECTRONICS | Alldatasheet
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Technical content
256 Kbit (32Kb x 8) Low Voltage UV EPROM and OTP EPROM
n 2.7V to 3.6V SUPPLY VOLTAGE in READ OPERATION n ACCESS TIME: –7 0 n s a t VCC = 3.0V to 3.6V –8 0 n s a t VCC = 2.7V to 3.6V n PIN COMPATIBLE with M27C256B n LOW POWER CONSUMPTION: –1 5µA max Standby Current – 15mA max Active Current at 5MHz n PROGRAMMING TIME 100 µs/byte n HIGH RELIABILITY CMOS TECHNOLOGY – 2,000V ESD Protection – 200mA Latchup Protection Immunity n ELECTRONIC SIGNATURE – Manufacturer Code: 20h – Device Code: 3Dh
DESCRIPTION
The M27W256 is a low voltage 256 Kbit EPROM offered in the two ranges UV (ultra violet erase) and OTP (one time programmable). It is ideally suited for microprocessor systems and is orga- nized as 32,768 by 8 bits. The M27W256 operates in the read mode with a supply voltage as low as 3V. The decrease in op- erating power allows either a reduction of the size of the battery or an increase in the time between battery recharges. The FDIP28W (window ceramic frit-seal package) has a transparent lid which allows the user to ex- pose the chip to ultraviolet light to erase the bit pat- tern. A new pattern can then be written to the device by following the programming procedure. For applications where the content is programmed only one time and erasure is not required, the M27W256 is offered in PDIP28, PLCC32 and TSOP28 (8 x 13.4 mm) packages. Figure 1. Logic Diagram
1 VPP
Table 1. Signal Names
Table 2. Absolute Maximum Ratings(1)
- Minimum DC voltage on Input or Output is –0.5V with possible undershoot to –2.0V for a period less than 20ns. Maximum DC
voltage on Output is VCC +0.5V with possible overshoot to VCC +2V for a period less than 20ns. Table 3. Operating Modes Note: X = VIH or VIL,V ID = 12V ± 0.5V. Table 4. Electronic Signature
Table 7. Read Mode DC Characteristics(1) Note: 1. VCC must be applied simultaneously with or before VPP and removed simultaneously or after VPP .
- Maximum DC voltage on Output is VCC +0.5V.
Table 8. Read Mode AC Characteristics(1) Note: 1. VCC must be applied simultaneously with or before VPP and removed simultaneously or after VPP .
- Sampled only, not 100% tested.
- Speed obtained with High Speed AC measurement conditions.
Figure 5. Read Mode AC Waveforms data is desired from a particular memory device. caused by the inductive effects of PCB traces.
Table 9. Programming Mode DC Characteristics(1) Note: VCC must be applied simultaneously with or before VPP and removed simultaneously or after VPP . Table 10. Programming Mode AC Characteristics(1) Note: VCC must be applied simultaneously with or before VPP and removed simultaneously or after VPP . ly programming ’0’s into the desired bit locations.
The M27W256 can be directly programmed in the application circuit. See the relevant Application Note AN620. Electronic Signature The Electronic Signature (ES) mode allows the reading out of a binary code from an EPROM that will identify its manufacturer and type. This mode is intended for use by programming equipment to automatically match the device to be programmed with its corresponding programming algorithm. The ES mode is functional in the 25°C ± 5°C am- bient temperature range that is required when pro- gramming the M27W256. To activate the ES mode, the programming equipment must force 11.5V to 12.5V on address line A9 of the M27W256, with V CC =V PP = 5V. Two identifier bytes may then be sequenced from the device out- puts by toggling address line A0 from VILto VIH. All other address lines must be held at VIL during Electronic Signature mode. Byte 0 (A0 = VIL) rep- resents the manufacturer code and byte 1 (A0 = VIH) the device identifier code. For the STMicroelectronics M27W256, these two identifier bytes are given in Table 4 and can be read-out on outputs Q7 to Q0. Note that the M27W256 and M27C256B have the same identifier bytes. ERASURE OPERATION (applies for UV EPROM) The erasure characteristics of the M27W256 is such that erasure begins when the cells are ex- posed to light with wavelengths shorter than ap- proximately 4000 Å. It should be noted that sunlight and some type of fluorescent lamps have wavelengths in the 3000-4000 Å range. Research shows that constant exposure to room level fluo- rescent lighting could erase a typical M27W256 in about 3 years, while it would take approximately 1 week to cause erasure when exposed to direct sunlight. If the M27W256 is to be exposed to these types of lighting conditions for extended periods of time, it is suggested that opaque labels be put over the M27W256 window to prevent unintentional erasure. The recommended erasure procedure for the M27W256 is exposure to short wave ultraviolet light which has wavelength 2537Å. The integrated dose (i.e. UV intensity x exposure time) for erasure should be a minimum of 15 W-sec/cm 2. The era- sure time with this dosage is approximately 15 to 20 minutes using an ultraviolet lamp with 12000 µW/cm 2 power rating. The M27W256 should be placed within 2.5 cm (1 inch) of the lamp tubes during the erasure. Some lamps have a filter on their tubes which should be removed before era- sure.
Table 11. Ordering Information Scheme Note: 1. High Speed, see AC Characteristics section for further information.
- This speed also guarantees 70ns access time at VCC = 3.0V to 3.6V.
- These speeds are replaced by the 100ns.
- Packages option available on request. Please contact STMicroelectronics local Sales Office.
vice, please contact the STMicroelectronics Sales Office nearest to you.
Table 12. FDIP28W - 28 pin Ceramic Frit-seal DIP, with window, Package Mechanical Data Figure 8. FDIP28W - 28 pin Ceramic Frit-seal DIP, with window, Package Outline
Table 13. PDIP28 - 28 pin Plastic DIP, 600 mils width, Package Mechanical Data Figure 9. PDIP28 - 28 pin Plastic DIP, 600 mils width, Package Outline
Table 14. PLCC32 - 32 lead Plastic Leaded Chip Carrier, Package Mechanical Data Figure 10. PLCC32 - 32 lead Plastic Leaded Chip Carrier, Package Outline
Figure 11. TSOP28 - 28 lead Plastic Thin Small Outline, 8 x 13.4 mm, Package Outline Table 15. TSOP28 - 28 lead Plastic Thin Small Outline, 8 x 13.4 mm, Package Mechanical Data
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