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DS4000EC/WBGA

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DS4000 Digitally Controlled TCXO
7 of 16
TEMPERATURE-COMPENSATED CRYSTAL OSCILLATOR
The DS4000 can either function as a standalone TCXO or as a digitally controlled TCXO. When used as a
standalone TCXO, the only requirements needed to function properly are power, ground, and an output. However,
the 2-wire interface must be used to tune (push and pull) the crystal.
The DS4000 is capable of supplying two different outputs, F
1
and F
2
.
1) F
1
is the base frequency of the crystal unit inside of the device. The output type is a CMOS square wave.
2) F
2
is a programmable frequency output. The frequency select register can program this output to an integer
division of the base (F
1
) frequency. The duty cycle (DC) bit determines if the output is an n + 1 or a 2(n + 1)
division of F
1
.
F
2
FREQUENCY SELECT REGISTER (FSR) (5Dh)
Bit
7 6 5 4 3 2 1 0
Name D7 D6 D5 D4 D3 D2 D1 D0
Default 0 0 0 0 0 0 0 0
F
2
= F
1
/ (FSR value + 1); with DC = 0
F
2
= F
1
/ [2 x (FSR value + 1)]; with DC = 1
TCXO CONTROL REGISTER (60h)
Bit
7 6 5 4 3 2 1 0
Name X X X X F
2
OE F
1
OE F
T
DC
Default 0 0 0 0 0 0 0 0
DC, Duty Cycle Bit: If 50% duty cycle is desired, then this bit must be set to logic 1. The default condition at
power-up is logic 0.
F
T
: This bit must be programmed by the user to 0.
F
1
OE, F
1
Output Enable Bit: This bit allows the user to disable/enable the F
1
output.
F
2
OE, F
2
Output Enable Bit: This bit allows the user to disable/enable the F
2
output.
DS4000 Digitally Controlled TCXO
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DIGITAL TUNING THE BASE CRYSTAL FREQUENCY
When using the 2-wire interface for tuning the base frequency, the frequency tuning register is used. The frequency
tuning register contains two’s complement data. The data is used to add or subtract an offset from the crystal
loading register. When the tuning register is programmed with a value, the next temperature-update cycle sums the
programmed value with the factory-compensated value. This allows the user/system to digitally control the base
frequency by a microcontroller using the 2-wire protocol.
FREQUENCY TUNING REGISTER (66h)
Bit
7 6 5 4 3 2 1 0
Name SIGN FO6 FO5 FO4 FO3 FO2 FO1 FO0
Default 0 0 0 0 0 0 0 0
FOS[6:0], Frequency Offset: These bits are used to tune the base crystal frequency. Each bit represents
approximately 0.08ppm and, therefore, for a value of 07FH, pushes or pulls the base frequency by approximately
10.16ppm.
SIGN, Sign Bit: This bit is used to determine whether to add or subtract the frequency offset from the crystal
loading.
Table 1. Frequency Tuning Relationship
CALCULATED
FREQUENCY OFFSET
(ppm)
DIGITAL DATA
(Binary)
DIGITAL DATA
(hex)
-10.16 0111 1111 7Fh
-8.00 0110 0100 64h
-5.28 0100 0010 42h
-1.84 0001 0111 17h
-0.08 0000 0001 01h
0.0 0000 0000 00h
+0.08 1111 1111 FFh
+1.84 1110 1000 E8h
+5.28 1011 0011 B3h
+8.00 1001 1100 9Ch
+10.16 1000 0000 80h
DS4000 Digitally Controlled TCXO
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DIGITAL TEMPERATURE SENSOR
The digital temperature sensor provides 10-bit temperature readings that indicate the temperature of the device.
Temperature readings are communicated from the DS4000 over a 2-wire serial interface. No additional
components are required. The DS4000 has an external address bit that allows a user to choose the slave address
from two possible values.
The factory-calibrated temperature sensor requires no external components. Upon power-up, the DS4000 starts
performing temperature conversions with a resolution of 10 bits (+0.25°C resolution). Following an 8-bit command
protocol, temperature data can be read over the 2-wire interface. The host can periodically read the value in the
temperature register, which contains the last completed conversion. As conversions are performed in the
background, reading the temperature register does not affect the conversion in progress.
READING TEMPERATURE
The DS4000 measures temperature through the use of an on-chip temperature-measurement technique with an
operation range from 0°C to +70°C (commercial) or -40°C to +85°C (industrial). The device performs continuous
conversions with the most recent result being stored in the temperature register. The digital temperature is
retrieved from the temperature register using the READ TEMPERATURE command, as described in detail in the
following paragraphs.
Table 2 shows the exact relationship of output data to measured temperature. The data is transmitted serially over
the 2-wire serial interface, MSB first. The MSB of the temperature register contains the “sign” (S) bit, denoting
whether the temperature is positive or negative. For Fahrenheit usage, a lookup table or conversion routine must
be used.
TEMPERATURE/DATA RELATIONSHIP (UNIT = °C)
MSB (64h)
BIT 7 BIT 6 BIT 5 BIT 4 BIT 3 BIT 2 BIT 1 BIT 0
S 2
6
2
5
2
4
2
3
2
2
2
1
2
0
LSB (65h)
BIT 7 BIT 6 BIT 5 BIT 4 BIT 3 BIT 2 BIT 1 BIT 0
2
-1
2
-2
0 0 0 0 0 0
Table 2. Temperature/Data Relationship
TEMPERATURE
(°C)
DIGITAL OUTPUT
(Binary)
DIGITALOUTPUT
(hex)
+85 0101 0101 0000 0000 5500h
+75 0100 1011 0000 0000 4B00h
+0.5 0000 0000 1000 0000 0080h
0 0000 0000 0000 0000 0000h
-0.5 1111 1111 1000 0000 FF80h
-20 1110 1100 0000 0000 EC00h
-40 1101 1000 0000 0000 D800h
Note: Internal power dissipation raises the temperature above the ambient. The delta between ambient and the die temperature depends on
power consumption, PC board layout, and airflow.
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DS4000EC/WBGA

Mfr. #:
Buy DS4000EC/WBGA
Manufacturer:
Maxim Integrated
Description:
TCXO Oscillators
Lifecycle:
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