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参数资料
| 型号： | FM31L276-GTR |
| 元件分类： | 消费家电 |
| 英文描述： | SPECIALTY CONSUMER CIRCUIT, PDSO14 |
| 封装： | GREEN, MS-012AB, SOIC-14 |
| 文件页数： | 24/26页 |
| 文件大小： | 716K |
| 代理商： | FM31L276-GTR |
FM31L278/L276/L274/L272 - 3V I2C Companion
Rev. 2.0
Jan. 2011
Page 7 of 26
to be loaded into the timekeeper core. W is used for
writing new time values. Users should be certain not
to load invalid values, such as FFh, to the
timekeeping registers. Updates to the timekeeping
core occur continuously except when locked.
Backup Power
The real-time clock/calendar is intended to be
permanently powered. When the primary system
power fails, the voltage on the VDD pin will drop.
When VDD is less 2.5V the RTC (and event counters)
will switch to the backup power supply on VBAK. The
clock operates at extremely low current in order to
maximize battery or capacitor life. However, one of
the advantages of combining a clock function with
the F-RAM memory is that data is not lost regardless
of the backup power source.
The IBAK current varies with temperature and voltage
(see DC parametric table). The following graph
shows IBAK as a function of VBAK. These curves are
useful for calculating backup time when a capacitor
is used as the VBAK source.
Figure 7. IBAK vs. VBAK Voltage
The minimum VBAK voltage varies linearly with
temperature. The user can expect the minimum VBAK
voltage to be 1.23V at +85°C and 1.90V at -40°C.
The tested limit is 1.55V at +25°C. The minimum
VBAK voltage has been characterized at -40°C and
+85°C but is not 100% tested.
Figure 8. VBAK (min.) vs. Temperature
Trickle Charger
To facilitate capacitor backup the VBAK pin can
optionally provide a trickle charge current. When the
VBC bit, register 0Bh bit 2, is set to ‘1’, the VBAK pin
will source approximately 80 A until VBAK reaches
VDD. This charges the capacitor to VDD without an
external diode and resistor charger. There is a Fast
Charge mode which is enabled by the FC bit (register
0Bh, bit 5). In this mode the trickle charger current is
set to approximately 1 mA, allowing a large backup
capacitor to charge more quickly.
In the case where no backup supply is used, the VBAK
pin should be tied to VSS. Be sure to turn off the
trickle charger (VBC=0), otherwise charger current
will be shunted to ground from VDD.
Note: systems using lithium batteries should clear
the VBC bit to 0 to prevent battery charging. The
VBAK circuitry includes an internal 1 K
series
resistor as a safety element. The trickle charger is UL
Recognized.
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相关代理商/技术参数 |
参数描述 |
|---|---|
| FM31L278 | 制造商:RAMTRON 制造商全称:RAMTRON 功能描述:3V Integrated Processor Companion with Memory |
| FM31L278_11 | 制造商:RAMTRON 制造商全称:RAMTRON 功能描述:3V Integrated Processor Companion with Memory |
| FM31L278G | 制造商:Cypress Semiconductor 功能描述: |
| FM31L278-G | 功能描述:监控电路 256K w/RTC Pwr Mon WDT Bat Sw PF RoHS:否 制造商:STMicroelectronics 监测电压数: 监测电压: 欠电压阈值: 过电压阈值: 输出类型:Active Low, Open Drain 人工复位:Resettable 监视器:No Watchdog 电池备用开关:No Backup 上电复位延迟（典型值）:10 s 电源电压-最大:5.5 V 最大工作温度:+ 85 C 安装风格:SMD/SMT 封装 / 箱体:UDFN-6 封装:Reel |
| FM31L278-GTR | 功能描述:监控电路 256K w/RTC Pwr Mon WDT Bat Sw PF RoHS:否 制造商:STMicroelectronics 监测电压数: 监测电压: 欠电压阈值: 过电压阈值: 输出类型:Active Low, Open Drain 人工复位:Resettable 监视器:No Watchdog 电池备用开关:No Backup 上电复位延迟（典型值）:10 s 电源电压-最大:5.5 V 最大工作温度:+ 85 C 安装风格:SMD/SMT 封装 / 箱体:UDFN-6 封装:Reel |
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