M40Z300AV STMICROELECTRONICS | Alldatasheet
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Technical content
DESCRIPTION
The M40Z300AV NVRAM SUPERVISOR is a self- contained device which converts a standard low- power SRAM into a non-volatile memory. A preci- sion voltage reference and comparator monitors the VCC input for an out-of-tolerance condition. When an invalid VCC condition occurs, the condi- tioned chip enable outputs (E1CON to E4CON) are forced inactive to write-protect the stored data in the SRAM. During a power failure, the SRAM is switched from the VCC pin to the lithium cell within the SNAPHAT® to provide the energy required for data retention. On a subsequent power-up, the SRAM remains write protected until a valid power condition returns. The 28-pin, 330mil SOIC provides sockets with gold plated contacts for direct connection to a sep- arate SNAPHAT housing containing the battery. The SNAPHAT housing has gold plated pins which mate with the sockets, ensuring reliable connection. The housing is keyed to prevent im- proper insertion. This unique design allows the SNAPHAT battery package to be mounted on top of the SOIC package after the completion of the surface mount process which greatly reduces the board manufacturing process complexity of either directly soldering or inserting a battery into a sol- dered holder. Providing non-volatility becomes a “SNAP.” The 16-pin SOIC provides battery pins for an external user-supplied battery. Insertion of the SNAPHAT housing after reflow prevents potential battery damage due to the high temperatures required for device surface-mount- ing. The SNAPHAT housing is also keyed to pre- vent reverse insertion. The 28-pin SOIC and battery packages are shipped separately in plastic anti-static tubes or in Tape & Reel form. For the 28-lead SOIC, the bat- tery/crystal package (e.g., SNAPHAT) part num- ber is “M4ZXX-BR00SH” (see Table 13., page 18). Caution: Do not place the SNAPHAT battery top in conductive foam, as this will drain the lithium button-cell battery. Figure 3. Logic Diagram Note: 1. For 16-pin SOIC package only.
- THS pin must be connected to VSS.
Table 1. Signal Names Note: 1. THS pin must be connected to VSS.
- For M40Z300AV, B– must be connected to the negative
battery terminal only (not to Pin 8, VSS).
IOUT2 (see Table 6., page 11). stabilization (see Figure 11., page 12). Table 2. Truth Table Figure 7. Address-Decode Time
Data Retention Lifetime Calculation Most low power SRAMs on the market today can be used with the M40Z300AV NVRAM SUPERVI- SOR. There are, however some criteria which should be used in making the final choice of which SRAM to use. The SRAM must be designed in a way where the chip enable input disables all other inputs to the SRAM. This allows inputs to the M40Z300AV and SRAMs to be “Don't care” once VCC falls below VPFD(min). The SRAM should also guarantee data retention down to VCC = 2.0V. The chip enable access time must be sufficient to meet the system needs with the chip enable propaga- tion delays included. If the SRAM includes a sec- ond chip enable pin (E2), this pin should be tied to VOUT. If data retention lifetime is a critical parameter for the system, it is important to review the data reten- tion current specifications for the particular SRAMs being evaluated. Most SRAMs specify a data retention current at 3.0V. Manufacturers gen- erally specify a typical condition for room temper- ature along with a worst case condition (generally at elevated temperatures). The system level re- quirements will determine the choice of which val- ue to use. The data retention current value of the SRAMs can then be added to the IBAT value of the M40Z300AV to determine the total current requirements for data retention. The available battery capacity for the SNAPHAT® of your choice can then be divided by this current to determine the amount of data re- tention available (see Table 13., page 18). CAUTION: Take care to avoid inadvertent dis- charge through VOUT and E1CON - E4CON after battery has been attached. For a further more detailed review of lifetime calcu- lations, please see Application Note AN1012. Power-on Reset Output All microprocessors have a reset input which forc- es them to a known state when starting. The M40Z300AV has a reset output (RST) pin which is guaranteed to be low within tWPT of VPFD (see Ta- ble 7., page 13). This signal is an open drain con- figuration. An appropriate pull-up resistor should be chosen to control the rise time. This signal will be valid for all voltage conditions, even when VCC equals VSS. Once VCC exceeds the power failure detect volt- age VPFD, an internal timer keeps RST low for tREC to allow the power supply to stabilize. Battery Low Pin The M40Z300AV automatically performs battery voltage monitoring upon power-up, and at factory- programmed time intervals of at least 24 hours. The Battery Low (BL) pin will be asserted if the battery voltage is found to be less than approxi- mately 2.5V. The BL pin will remain asserted until completion of battery replacement and subse- quent battery low monitoring tests, either during the next power-up sequence or the next scheduled 24-hour interval. If a battery low is generated during a power-up se- quence, this indicates that the battery is below 2.5V and may not be able to maintain data integrity in the SRAM. Data should be considered suspect, and verified as correct. A fresh battery should be installed. If a battery low indication is generated during the 24-hour interval check, this indicates that the bat- tery is near end of life. However, data is not com- promised due to the fact that a nominal VCC is supplied. In order to insure data integrity during subsequent periods of battery back-up mode, the battery should be replaced. The SNAPHAT® top should be replaced with valid VCC applied to the device. The M40Z300AV only monitors the battery when a nominal VCC is applied to the device. Thus appli- cations which require extensive durations in the battery back-up mode should be powered-up peri- odically (at least once every few months) in order for this technique to be beneficial. Additionally, if a battery low is indicated, data integrity should be verified upon power-up via a checksum or other technique. The BL pin is an open drain output and an appropriate pull-up resistor to VCC should be chosen to control the rise time.
VSS (cathode connected to VCC, anode to VSS). Figure 8. Supply Voltage Protection
Table 3. Absolute Maximum Ratings
- For SO package, standard lead finish: Reflow at peak temperature of 225°C (total thermal budget not to exceed 180°C for between
- For SO package, Lead-free (Pb-free) lead finish: Reflow at peak temperature of 260°C (total thermal budget not to exceed 245°C
for greater than 30 seconds). CAUTION: Negative undershoots below –0.3V are not allowed on any pin while in the Battery Back-up mode. CAUTION: Do NOT wave solder SOIC to avoid damaging SNAPHAT sockets.
tions when using the quoted parameters. Table 4. DC and AC Measurement Conditions Note: Output High Z is defined as the point where data is no longer driven. Figure 9. AC Testing Load Circuit Table 5. Capacitance Note: 1. Sampled only, not 100% tested.
Table 6. DC Characteristics Note: 1. Valid for Ambient Operating Temperature: TA = 0 to 70°C or –40 to 85°C; VCC = 3.0 to 3.6V (except where noted).
- For RST & BL pins (Open Drain).
- Chip Enable outputs (E1CON - E4CON) can only sustain CMOS leakage currents in the battery back-up mode.
Higher leakage currents will reduce battery life.
- Measured with VOUT and E1CON - E4CON open.
- THS pin must ben tied to VSS.
Table 7. Power Down/Up Mode AC Characteristics Note: 1. Valid for Ambient Operating Temperature: TA = 0 to 70°C or –40 to 85°C; VCC = 3.0 to 3.6V (except where noted).
- VPFD (max) to VPFD (min) fall time of less than tF may result in deselection/write protection not occurring until 200 µs after VCC
- VPFD (min) to VSS fall time of less than tFB may cause corruption of RAM data.
- tREC (min) = 20ms for industrial temperature Grade 6 device.
Figure 12. SOH28 – 28-lead Plastic Small Outline, 4-socket battery SNAPHAT, Package Outline Note: Drawing is not to scale. Table 8. SOH28 – 28-lead Plastic Small Outline, battery SNAPHAT, Package Mechanical Data
Figure 13. SH – 4-pin SNAPHAT Housing for 48mAh Battery, Package Outline Note: Drawing is not to scale. Table 9. SH – 4-pin SNAPHAT Housing for 48mAh Battery, Package Mechanical Data
Figure 14. SH – 4-pin SNAPHAT Housing for 120mAh Battery, Package Outline Note: Drawing is not to scale. Table 10. SH – 4-pin SNAPHAT Housing for 120mAh Battery, Package Mechanical Data
Figure 15. SO16 – 16-lead Plastic Small Outline, 150 mils body width, Package Outline Note: Drawing is not to scale. Table 11. SO16 – 16-lead Plastic Small Outline, 150 mils body width, Package Mechanical Data
Table 12. Ordering Information Example “M4Zxx-BR00SH” in plastic tube or “M4Zxx-BR00SHTR” in Tape & Reel form.
- Contact Local Sales Office for availability of SNAPHAT (MH) package.
please contact the ST Sales Office nearest to you. Table 13. SNAPHAT® Battery Table Lithium Battery (48mAh) SNAPHAT SH M4Z32-BR00SH Lithium Battery (120mAh) SNAPHAT SH
REVISION HISTORY
Table 14. Document Revision History
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