FM33256B-G Integrated Processor Companion with F-RAM
Features
High Integration Device Replaces Multiple Parts
Serial Nonvolatile Memory
Real-time Clock (RTC) with Alarm
Low VDD Detection Drives Reset
Watchdog Window Timer
Early Power-Fail Warning/NMI
16-bit Nonvolatile Event Counter
Serial Number with Write-lock for Security
Ferroelectric Nonvolatile RAM
256Kb F-RAM
High Endurance 100 Trillion (1014) Read/Writes
38 year Data Retention (+75°C)
NoDelay™ Writes
Real-time Clock/Calendar
Backup Current at 2V, 1.15 µA (max.) at +25C
Seconds through Centuries in BCD format
Tracks Leap Years through 2099
Uses Standard 32.768 kHz Crystal
Software Calibration
Supports Battery or Capacitor Backup
Processor Companion
Active-low Reset Output for VDD and Watchdog
Programmable Low-VDD Reset Thresholds
Manual Reset Filtered and Debounced
Programmable Watchdog Window Timer
Nonvolatile Event Counter Tracks System Intrusions or other Events
Comparator for Power-Fail Interrupt or Other Use
64-bit Programmable Serial Number with Lock
Fast SPI Interface
Up to 16 MHz Maximum Bus Frequency
RTC, Supervisor Controlled via SPI Interface
SPI Mode 0 & 3 (CPOL, CPHA=0,0 & 1,1) Easy to Use
Configuration
Operates from 2.7 to 3.6V
Small Footprint “Green” 14-pin SOIC (-G)
Low Operating Current
-40°C to +85°C Operation
Underwriters Laboratory (UL) Recognized
Description
The FM33256B device integrates F-RAM memory with the most commonly
needed functions for processor-based systems. Major features
include nonvolatile memory, real-time clock, low-VDD reset,
watchdog timer, nonvolatile event counter, lockable 64-bit serial
number area, and general purpose comparator that can be used for a
power-fail (NMI) interrupt or other purpose. The device operate
from 2.7 to 3.6V. The FM33256B provides 256Kb memory capacity of
nonvolatile F-RAM. Fast write speed and unlimited endurance allow
the memory to serve as extra RAM or conventional nonvolatile
storage. This memory is truly nonvolatile rather than battery
backed. The real-time clock (RTC) provides time and date
information in BCD format. It can be permanently powered from
external backup voltage source, either a battery or a capacitor.
The timekeeper uses a common external 32.768 kHz crystal and
provides a calibration mode that allows software adjustment of
timekeeping accuracy. The processor companion includes commonly
needed CPU support functions. Supervisory functions include a reset
output signal controlled by either a low VDD condition or a
watchdog timeout. /RST goes active when VDD drops below a
programmable threshold and remains active for 100 ms (max.) after
VDD rises above the trip point. A programmable watchdog timer runs
from 60 ms to 1.8 seconds. The timer may also be programmed for a
delayed start, which functions as a window timer. The watchdog
timer is optional, but if enabled it will assert the reset signal
for 100 ms if not restarted by the host within the time window. A
flag-bit indicates the source of the reset. A comparator on PFI
compares an external input pin to the onboard 1.5V reference. This
is useful for generating a power-fail interrupt (NMI) but can be
used for any purpose. The family also includes a programmable
64-bit serial number that can be locked making it unalterable.
Additionally it offers an event counter that tracks the number of
rising or falling edges detected on a dedicated input pin. The
counter can be programmed to be non-volatile under VDD power or
battery-backed using only VBAK. If VBAK is connected to a battery
or capacitor, then events will be counted even in the absence of
VDD.
Pin Name | Type P | Pin Description |
---|
/CS | Input | Chip Select: This active low input activates the device. When high,
the device enters lowpower standby mode, ignores the SCK and SI
inputs, and the SO output is tri-stated. When low, the device
internally activates the SCK signal. A falling edge on /CS must
occur prior to every op-code. |
SCK | Input | Serial Clock: All I/O activity is synchronized to the serial clock.
Inputs are latched on the rising edge and outputs occur on the
falling edge. Since the device is static, the clock frequency may
be any value between 0 and 16 MHz and may be interrupted at any
time. |
SI | Input | Serial Input: All data is input to the device on this pin. The pin
is sampled on the rising edge of SCK and is ignored at other times.
It should always be driven to a valid logic level to meet IDD
specifications. The SI pin may be connected to SO for a single pin
data interface. |
SO | Output | Serial Output: This is the data output pin. It is driven during a
read and remains tri-stated at all other times. Data transitions
are driven on the falling edge of the serial clock. The SO pin may
be connected to SI for a single pin data interface |
CNT | Input | Event Counter Input: This input increments the counter when an edge
is detected on this pin. The polarity is programmable and the
counter value is nonvolatile or battery-backed, depending on the
mode. This pin should be tied to ground if unused. |
ACS | Output | Alarm/Calibration/SquareWave: This is an open-drain output that
requires an external pullup resistor. In normal operation, this pin
acts as the active-low alarm output. In Calibration mode, a 512 Hz
square-wave is driven out. In SquareWave mode, the user may select
a frequency of 1, 512, 4096, or 32768 Hz to be used as a continuous
output. The SquareWave mode is entered by clearing the AL/SW and
CAL bits in register 18h |
X1, X2 | I/O | 32.768 kHz crystal connection (see Crystal Type section for
suggestions). See AN407 app. note for details on how to connect
external oscillator. |
/RST | I/O | Reset: This active-low output is open drain with weak pull-up. It
is also an input when used as a manual reset. This pin should be
left floating if unused. |
PFI | Input | Early Power-fail Input: Typically connected to an unregulated power
supply to detect an early power failure. This pin must be tied to
ground if unused |
PFO | Output | Early Power-fail Output: This pin is the early power-fail output
and is typically used to drive a microcontroller NMI pin. PFO
drives low when the PFI voltage is <1.5V. |
VBAK | Supply | Backup supply voltage: A 3V battery or a large value capacitor. If
no backup supply is used, this pin should be tied to VSS and the
VBC bit should be cleared. The trickle charger is UL recognized and
ensures no excessive current when using a lithium battery. |
VDD | Supply | Supply Voltage |
VSS | Supply | Ground |
Stock Offer (Hot Sell)
Part Number | Qty | mfg | D/C | Package |
LM22676TJE-ADJ | 6794 | TI | 13+ | TO-263 |
LM22777TJ-ADJ | 5048 | NS | 16+ | TO-263 |
LM239APT | 4458 | ST | 13+ | TSSOP-14 |
LM25011MY/NOPB | 3243 | TI | 16+ | MSOP-10 |
LM25037MTX | 4474 | TI | 09+ | TSSOP-16 |
LM25119PSQ/NOPB | 1820 | TI | 15+ | WQFN-32 |
LM25575MHX | 3711 | TI | 12+ | TSSOP-16 |
LM25576MHX | 5141 | TI | 14+ | TSSOP-20 |
LM2575D2T-3.3R4G | 18153 | ON | 11+ | TO-263 |
LM2575HVT-5.0 | 13120 | NS | 15+ | TO-220 |
LM2575SX-5.0 | 22261 | NS | 16+ | TO-263 |
LM2576-5.0WU | 4267 | MICREL | 14+ | TO-263 |
LM2576D2TR4-5G | 5273 | ON | 14+ | TO-263 |
LM2576HVSX-ADJ | 6468 | TI | 15+ | TO-263 |
LM2576HVT-ADJ | 21640 | NS | 16+ | TO-220 |
LM2576SX-1.2 | 18871 | NSC | 13+ | TO263-5 |
LM2577T-ADJ | 4542 | NS | 12+ | TO-220-5 |
LM2586SX-ADJ | 2498 | NS | 07+ | TO-263-7 |
LM2588T-5.0 | 3655 | TI | 15+ | TO-220-7 |
LM258DR | 69000 | TI | 16+ | SOP-8 |
LM258DT | 70000 | ST | 13+ | SOP-8 |
LM2594HVM-5.0 | 3314 | NS | 13+ | SOP-8 |
LM2596HVT-ADJ | 21711 | NS | 14+ | TO-220 |
LM2622MM-ADJ | 2888 | NSC | 08+ | MSOP-8 |
LM2651MTCX-ADJ | 8710 | NS | 04+ | TSSOP |
LM2662MX | 5344 | TI | 16+ | SOP-8 |
LM2663M | 6856 | NS | 16+ | SOP-8 |
LM2675MX-5.0 | 5274 | TI | 16+ | SOP-8 |
LM2675MX-ADJ | 5415 | TI | 15+ | SOP-8 |
LM2734YMK | 12799 | TI | 16+ | SOT23-6 |
LM2767M5X | 6927 | NSC | 16+ | SOT23-5 |
LM2825N-ADJ | 1525 | NSC | 06+ | DIP-24 |
LM2842YMK-ADJL | 4655 | TI | 16+ | SOT23-6 |
LM285MX-1.2 | 5929 | NS | 16+ | SOP-8 |
LM2901DR2G | 104000 | ON | 13+ | SOP |
LM2902DR2G | 77000 | ON | 15+ | SOP |
LM2903DR2G | 107000 | ON | 15+ | SOP |
LM2903IMX | 13191 | FSC | 11+ | SOP-8 |
LM2904DR2G | 82000 | ON | 16+ | SOP-8 |
LM2904MX | 11700 | NS | 15+ | SOP-8 |
LM2904P | 20000 | TI | 16+ | TSSOP-8 |
LM2904QPWRQ1 | 6065 | TI | 14+ | TSSOP-8 |
LM2907N-8 | 8781 | NS | 97+ | DIP-8 |
LM2917N-8 | 6580 | NS | 13+ | DIP-8 |
LM2931AD-5.0R2G | 19723 | ON | 16+ | SOP-8 |
LM2931CDR2G | 14829 | ON | 16+ | SOP-8 |
LM2931CDR2G | 10000 | ON | 15+ | SOP-8 |
LM2936MPX-3.3 | 9351 | TI | 14+ | SOT-223 |
LM2936Z-5.0 | 3406 | NS | 05+ | TO-92 |
LM2937ESX-3.3 | 9135 | NSC | 07+ | TO-263 |
LM2937IMPX-3.3 | 1862 | TI | 16+ | SOT-223 |
LM2940CSX-5.0 | 8095 | NS | 14+ | TO-263 |
LM2940S-5.0 | 10367 | NS | 16+ | TO-263 |
LM2940SX-5.0 | 8852 | NS | 15+ | TO-263 |
LM3102MHX | 4578 | NS | 1540+ | TSSOP-20 |
LM311DR | 58000 | TI | 13+ | SOP-8 |
LM311DT | 60000 | ST | 16+ | SOP-8 |
LM317AMDT | 52000 | NS | 13+ | TO-252 |
LM317BTG | 13900 | ON | 11+ | TO-220 |
LM317DCYR | 20007 | TI | 16+ | SOT-223 |
LM317LD13TR | 17000 | ST | 16+ | SOP-8 |
LM317LZ | 21782 | TI | 15+ | TO-92 |
LM317MBSTT3G | 4644 | ON | 15+ | SOT-223 |
LM317MDTRKG | 5965 | ON | 14+ | TO-252 |
LM317MDT-TR | 59000 | ST | 15+ | TO-252 |
LM317MDTX | 93000 | NS | 14+ | TO-252 |
LM318P | 3377 | TI | 03+ | DIP-8 |
LM321MFX | 6036 | TI | 10+ | SOT-23 |
LM324ADR | 66000 | TI | 16+ | SOP-14 |
LM324ADR2G | 11000 | ON | 14+ | SOP-14 |
LM324DR | 55000 | TI | 16+ | SOP-14 |