AS1541-BTST View Datasheet(PDF) - austriamicrosystems AG
Part Name
Description
MFG CO.
AS1541-BTST Datasheet PDF : 20 Pages
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AS1539/AS1541
Data Sheet - Application Information
Reading with Internal Reference On/Off
The internal reference defaults to off when the AS1539/AS1541 power is on. If the reference (internal or external) is
continuously turned on and off, a proper amount of settling time must be added before a normal conversion cycle can
be started. The exact amount of settling time needed varies depending on the reference capacitor. For example for a
reference capacitor of 4.7µF and considering the output impedance of the internal reference of 30Ω and the amount of
time to fully charge the capacitor will be 1.4ms. If the reference capacitor is not fully discharged this time can be
reduced greatly.
Figure 29 shows the correct internal reference enable sequence before issuing the typical read sequences required for
the mode when an internal reference is used.
Note: Typical read sequences can be re-used once the internal reference has settled.
Figure 29. Internal Reference Enable Sequence and Typical Read Sequence
Internal-Reference Enable Sequence
Internal-Reference
Enable Settling Time
S 1 0 0 1 0 A1 A0 W A X X X X 1 X X X A P Wait until required settling time reached
Write-Addressing Byte
Command Byte
ADC Powerdown Mode
Typical Mode Read Sequence
Settled Internal Reference
ADC Sampling Mode
Sr 1 0 0 1 0 A1 A0 W A SD C2 C1 C0 1 PD0 X X A
Write-Addressing Byte
Command Byte
ADC Conversion Mode
Settled Internal Reference
ADC Powerdown Mode *
Sr 1 0 0 1 0 A1 A0 R A 0 0 0 0 D9 D8 D7 D6 A D5 D4 ... D0 D0 D0 N P **
Read-Addressing Byte
From Master to Slave
From Slave to Master
2 x (8-bits +ACK/NACK
* Dependant on powerdown selection
bits PD0 and PD1.
** To remain in HS mode, use repeated
STARTs instead of STOPs
Where:
A: Acknowledge (SDA Low)
N: Not Acknowledge (SDA High)
S: START Condition
P: STOP Condition
Sr: Repeated START Condition
W: 0 (Write)
R: 1 (Read)
X: Dont Care
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Revision 1.02
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