参数资料
型号: CAT525W
元件分类: 模拟信号调理
英文描述: SPECIALTY ANALOG CIRCUIT, PDSO20
封装: LEAD-FREE, SOIC-20
文件页数: 9/12页
文件大小: 97K
代理商: CAT525W
CAT525
6
Doc. No. 2001, Rev. E
As data transfers are edge triggered clean clock
transitions are necessary to avoid falsely clocking data
into the control registers. Standard CMOS and TTL logic
families work well in this regard and it is recommended
that any mechanical switches used for breadboarding or
device evaluation purposes be debounced by a flip-flop
or other suitable debouncing circuit.
VREF
VREF, the voltage applied between pins VREFH &VREFL,
sets the configured DPP’s Zero to Full Scale output
range where VREFL = Zero and VREFH = Full Scale. VREF
can span the full power supply range or just a fraction of
it. In typical applications VREFH &VREFL are connected
across the power supply rails. When using less than the
full supply voltage be mindfull of the limits placed on
VREFH and VREFL as specified in the References section
of DC Electrical Characteristics.
READY/
BUSY
When saving data to non-volatile memory, the Ready/
Busy ouput (RDY/
BSY) signals the start and duration of
the erase/write cycle. Upon receiving a command to
store data (PROG goes high) RDY/
BSY goes low and
remains low until the programming cycle is complete.
During this time the CAT525 will ignore any data
appearing at DI and no data will be output on DO.
RDY/
BSY is internally ANDed with a low voltage detector
circuit monitoring VDD. If VDD is below the minimum value
required for EEPROM programming, RDY/
BSY will
remain high following the program command indicating
a failure to record the desired data in non-volatile memory.
DATA OUTPUT
Data is output serially by the CAT525, LSB first, via the
Data Out (DO) pin following the reception of a start bit
and two address bits by the Data Input (DI).
DO
becomes active whenever CS goes high and resumes
its high impedance Tri-State mode when CS returns low.
Tri-Stating the DO pin allows several 525s to share a
single serial data line and simplifies interfacing multiple
525s to a microprocessor.
WRITING TO MEMORY
Programming the CAT525’s non-volatile memory is
accomplished through the control signals: Chip Select
(CS) and Program (PROG). With CS high, a start bit
followed by a two bit DPP address and eight data bits are
clocked into the DPP wiper control register via the DI pin.
Data enters on the clock’s rising edge. The DPP output
changes to its new setting on the clock cycle following
D7, the last data bit.
Programming is accomplished by bringing PROG high
sometime after the start bit and at least 150 ns prior to the
rising edge of the clock cycle immediately following the
D7 bit. Two clock cycles after the D7 bit the DPP control
register will be ready to receive the next set of address
and data bits. The clock must be kept running throughout
the programming cycle. Internal control circuitry takes
care of generating and ramping up the programming
voltage for data transfer to the non-volatile memory
cells.
The CAT525’s non-volatile memory cells will
endure over 100,000 write cycles and will retain data for
a minimum of 20 years without being refreshed.
READING DATA
Each time data is transferred into a DPP wiper control
register currently held data is shifted out via the D0 pin,
thus in every data transaction a read cycle occurs. Note,
however, that the reading process is destructive. Data
must be removed from the register in order to be read.
Figure 2 depicts a Read Only cycle in which no change
occurs in the DPP’s output. This feature allows
Ps to
poll DPPs for their current setting without disturbing the
output voltage but it assumes that the setting being read
is also stored in non-volatile memory so that it can be
restored at the end of the read cycle. In Figure 2 CS
returns low before the 13th clock cycle completes. In
doing so the non-volatile memory setting is reloaded into
the DPP wiper control register. Since this value is the
Figure 1. Writing to Memory
Figure 2. Reading from Memory
A0
A1
1
DO
DI
CS
PROG
DPP
OUTPUT
t
1
2
3
4
5
6
7
8
9
10
11
12
o
CURRENT
DPP VALUE
NON-VOLATILE
D0
D1
D2
D3
D4
D5
D6
D7
CURRENT DPP DATA
RDY/BSY
D0
D1
D2
D3
D4
D5
D6
D7
A0
A1
D0
D1
D2
D3
D4
D5
D6
D7
1
NEW DPP DATA
CURRENT DPP DATA
CURRENT
DPP VALUE
NON-VOLATILE
DPP
OUTPUT
PROG
DO
DI
CS
NEW
DPP VALUE
VOLATILE
NEW
DPP VALUE
NON-VOLATILE
t
1
2
3
4
5
6
7
8
9
10
11
12
N
N+1 N+2
o
RDY/BSY
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