Welcome to EDAboard.com

Welcome to our site! EDAboard.com is an international Electronics Discussion Forum focused on EDA software, circuits, schematics, books, theory, papers, asic, pld, 8051, DSP, Network, RF, Analog Design, PCB, Service Manuals... and a whole lot more! To participate you need to register. Registration is free. Click here to register now.

the Vref of sigma delta ADC

Status
Not open for further replies.

kuohsi

Member level 3
Joined
Dec 21, 2005
Messages
65
Helped
1
Reputation
2
Reaction score
0
Trophy points
1,286
Activity points
1,665
switched capacitor adc vref

hi all, I am a rookie of this board.
Does anyone know what is the Vref which in the attached Figure?
and how many amplitude of Vref?
thank you!
 

tsb_nph

Full Member level 2
Joined
Mar 9, 2005
Messages
127
Helped
23
Reputation
46
Reaction score
5
Trophy points
1,298
Location
USA
Activity points
2,820
sigma delta adc+ vref

kuohsi said:
hi all, I am a rookie of this board.
Does anyone know what is the Vref which in the attached Figure?
and how many amplitude of Vref?
thank you!

Hi,
The Vref shown in the figure is the voltage associated with the feedback DAC.
If the output of the comparator is high, +Vref/2 is selected and fed back to the switched capacitor filter,and when the comparatpr output is low, -Vref/2 is fed back.
Usually, the voltage is multiplied by a feedback coefficient (implemented as capacitor ratios in a switched capacitor implementation.
The choice of Vref depends upon the supply voltage in the technology, implementation etc.

Hope that helps.

Bharath
 

    kuohsi

    Points: 2
    Helpful Answer Positive Rating

kuohsi

Member level 3
Joined
Dec 21, 2005
Messages
65
Helped
1
Reputation
2
Reaction score
0
Trophy points
1,286
Activity points
1,665
sigma delta adc+vref

tsb_nph said:
kuohsi said:
hi all, I am a rookie of this board.
Does anyone know what is the Vref which in the attached Figure?
and how many amplitude of Vref?
thank you!

Hi,
The Vref shown in the figure is the voltage associated with the feedback DAC.
If the output of the comparator is high, +Vref/2 is selected and fed back to the switched capacitor filter,and when the comparatpr output is low, -Vref/2 is fed back.
Usually, the voltage is multiplied by a feedback coefficient (implemented as capacitor ratios in a switched capacitor implementation.
The choice of Vref depends upon the supply voltage in the technology, implementation etc.

Hope that helps.

Bharath


Thank you for your answer
An extra question!!
Can I directly contect supply voltage (ex:5v) to Vref?
i.e. Vref=5v -Vref=-5v ?
 

tsb_nph

Full Member level 2
Joined
Mar 9, 2005
Messages
127
Helped
23
Reputation
46
Reaction score
5
Trophy points
1,298
Location
USA
Activity points
2,820
kuohsi said:
tsb_nph said:
kuohsi said:
hi all, I am a rookie of this board.
Does anyone know what is the Vref which in the attached Figure?
and how many amplitude of Vref?
thank you!

Hi,
The Vref shown in the figure is the voltage associated with the feedback DAC.
If the output of the comparator is high, +Vref/2 is selected and fed back to the switched capacitor filter,and when the comparatpr output is low, -Vref/2 is fed back.
Usually, the voltage is multiplied by a feedback coefficient (implemented as capacitor ratios in a switched capacitor implementation.
The choice of Vref depends upon the supply voltage in the technology, implementation etc.

Hope that helps.

Bharath


Thank you for your answer
An extra question!!
Can I directly contect supply voltage (ex:5v) to Vref?
i.e. Vref=5v -Vref=-5v ?

Hi,
You can use supply voltage as Vref provided the amplifier can handle these voltage ranges. For ex, when you choose Vref to be +5 V, then that voltage goes as input to the operational amplifier in the figure (switched capacitor filter).
If there is any attenuation (ie, you implement a coefficient), then you can use supply voltage, else yuu might have use a different voltage.

Bharath
 

sunking

Advanced Member level 3
Joined
May 25, 2004
Messages
874
Helped
70
Reputation
140
Reaction score
23
Trophy points
1,298
Activity points
6,283
of course you cannt due to poor PSSR
 

fxxjssc

Member level 4
Joined
Jan 6, 2006
Messages
79
Helped
2
Reputation
4
Reaction score
0
Trophy points
1,286
Activity points
1,879
hi,
vref of ADC produced from your reference voltage is better.
 

Status
Not open for further replies.

Similar threads

Part and Inventory Search

Welcome to EDABoard.com

Sponsor

Top