- 您现在的位置：买卖IC网 > PDF目录67504 > FM3316-G SPECIALTY CONSUMER CIRCUIT, PDSO14 PDF资料下载
参数资料
| 型号： | FM3316-G |
| 元件分类： | 消费家电 |
| 英文描述： | SPECIALTY CONSUMER CIRCUIT, PDSO14 |
| 封装： | GREEN, MO-012AB, SOIC-14 |
| 文件页数： | 28/28页 |
| 文件大小： | 320K |
| 代理商： | FM3316-G |
第1页第2页第3页第4页第5页第6页第7页第8页第9页第10页第11页第12页第13页第14页第15页第16页第17页第18页第19页第20页第21页第22页第23页第24页第25页第26页第27页当前第28页
FM33256/FM3316 SPI Companion w/ FRAM
Rev. 2.0
Feb. 2009
Page 9 of 28
Backup Power
The real-time clock and alarm are intended to be
permanently powered. When the primary system
power fails, the voltage on the VDD pin will drop.
When the VDD voltage is less than VSW, the RTC
(and event counter) 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, an advantage of combining a clock
function with F-RAM memory is that data is not lost
regardless of the backup power source.
Trickle Charger
To facilitate capacitor backup, the VBAK pin can
optionally provide a trickle charge current. When the
VBC bit (register 18h bit 3) is set to a ‘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 18h, bit 2). 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 battery is used, the V
BAK
pin should be tied to VSS and VBC bit cleared.
!
! 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.
Calibration
When the CAL bit in register 00h is set to a ‘1’, the
clock enters calibration mode. The FM33xx devices
employ a digital method for calibrating the crystal
oscillator frequency. The digital calibration scheme
applies a digital correction to the RTC counters based
on the calibration settings, CALS and CAL.4-0. In
calibration mode (CAL=1), the ACS pin is driven
with a 512 Hz (nominal) square wave and the alarm
is temporarily unavailable. Any measured deviation
from 512 Hz translates into a timekeeping error. The
user
measures
the
frequency
and
writes
the
appropriate
correction
value
to
the
calibration
register. The correction codes are listed in the table
below. For convenience, the table also shows the
frequency error in ppm. Positive ppm errors require a
negative adjustment that removes pulses. Negative
ppm errors require a positive correction that adds
pulses. Positive ppm adjustments have the CALS
(sign) bit set to 1, where as negative ppm adjustments
have CALS = 0. After calibration, the clock will have
a maximum error of
± 2.17 ppm or ± 0.09 minutes
per month at the calibrated temperature.
The user will not be able to see the effect of the
calibration setting on the 512 Hz output.
The
addition or subtraction of digital pulses occurs after
the 512 Hz output.
The calibration setting is stored in F-RAM so it is not
lost should the backup source fail. It is accessed with
bits CAL.4-0 in register 01h. This value only can be
written when the CAL bit is set to a 1. To exit the
calibration mode, the user must clear the CAL bit to a
logic 0. When the CAL bit is 0, the ACS pin will
revert to the function according to Table 2.
Crystal Type
The crystal oscillator is designed to use a 12.5pF
crystal without the need for external components,
such as loading capacitors. The FM33xx device has
built-in loading capacitors that match the crystal.
If a 32.768kHz crystal is not used, an external
oscillator may be connected to the FM33xx. Apply
the oscillator to the X1 pin. Its high and low voltage
levels can be driven rail-to-rail or amplitudes as low
as approximately 500mV p-p.
To ensure proper
operation, a DC bias must be applied to the X2 pin.
It should be centered between the high and low levels
on the X1 pin.
This can be accomplished with a
voltage divider.
Figure 10. External Oscillator
In the example, R1 and R2 are chosen such that the
X2 voltage is centered around the oscillator drive
levels. If you wish to avoid the DC current, you may
choose to drive X1 with an external clock and X2
with an inverted clock using a CMOS inverter.
Layout Recommendations
The X1 and X2 crystal pins employ very high
impedance circuits and the oscillator connected to
these pins can be upset by noise or extra loading. To
reduce RTC clock errors from signal switching noise,
a guard ring should be placed around these pads and
the guard ring grounded. High speed SPI traces
X1
Vdd
FM33xx
R1
R2
X2
相关PDF资料 |
PDF描述 |
|---|---|
| FM33256-GTR | SPECIALTY CONSUMER CIRCUIT, PDSO14 |
| FM33256-G | SPECIALTY CONSUMER CIRCUIT, PDSO14 |
| FM4005-G | SPECIALTY CONSUMER CIRCUIT, PDSO14 |
| FME270-461/ES | 1 FUNCTIONS, 400 V, 1.5 A, DATA LINE FILTER |
| FME270-461V/ES | 1 FUNCTIONS, 400 V, 1.5 A, DATA LINE FILTER |
相关代理商/技术参数 |
参数描述 |
|---|---|
| FM3316-GTR | 功能描述:F-RAM 16K w/Pwr Mon WDT Bat Sw Pwr Fail RoHS:否 存储容量:512 Kbit 组织:64 K x 8 接口:SPI 工作电源电压:2 V to 3.6 V 工作温度范围:- 40 C to + 85 C 安装风格:SMD/SMT 封装 / 箱体:SOIC-8 封装:Tube 制造商:Cypress Semiconductor |
| FM33256 | 制造商:RAMTRON 制造商全称:RAMTRON 功能描述:3V Integrated Processor Companion with Memory |
| FM33256_09 | 制造商:RAMTRON 制造商全称:RAMTRON 功能描述:3V Integrated Processor Companion with Memory |
| FM33256B | 制造商:CYPRESS 制造商全称:Cypress Semiconductor 功能描述:3V Integrated Processor Companion with F-RAM |
| FM33256B-G | 功能描述:实时时钟 256Kb F-RAM Processor Companion RoHS:否 制造商:Microchip Technology 功能:Clock, Calendar. Alarm RTC 总线接口:I2C 日期格式:DW:DM:M:Y 时间格式:HH:MM:SS RTC 存储容量:64 B 电源电压-最大:5.5 V 电源电压-最小:1.8 V 最大工作温度:+ 85 C 最小工作温度: 安装风格:Through Hole 封装 / 箱体:PDIP-8 封装:Tube |
发布紧急采购，3分钟左右您将得到回复。