AN764 Datasheet, PDF (1/6 Pages) Silicon Laboratories – Faster conversion time

AN764
UPGRADING FROM THE Si7005 TO THE Si7015
1. Introduction
The Si7015 digital relative humidity and temperature sensor is a pin-for-pin and register-compatible upgrade for the
Si7005. The Si7015 fixes the I²C “Acknowledge” issue of the Si7005 (meaning it can share an I²C bus with other
devices that have different addresses without being shut down) and offers several other performance
improvements, most notably:
Operation to 1.9 V_DD
Faster conversion time
Lower V_DD current in operation
Much lower V_DD current when in standby mode (CS high)
This application note covers some detailed considerations for migrating from the Si7005 to the Si7015.
2. Hardware
The package dimensions and pin-out are identical; no changes are required to the PCB layout for the 4x4
QFN package.
The bypass capacitor that supports the Si7005's on-chip linear regulator, C1 in Figure 1, is no longer
required, but it can be left in place if desired.
The SDA and SCL pins of the Si7015 may not be driven to voltages above V_DD. Switching V_DD low was
possible with the Si7005, as shown in Figure 1. With the Si7015, switching V_DD low with SDA SCL high is
not possible, so it should be connected as shown in Figure 2. Because the Si7015's standby power
consumption is exceptionally low, it is not necessary to switch V_DD off to save power.
VDD
Port Pin
SCL
SDA
R3
15.0
R1
R2
10K
10K
1 _GND
2
DNC
3 _SCL
4 _SDA
5
DNC
6
DNC
U2
Si7005
DNC ¹⁸
17
DNC
DNC ¹⁶
CS ¹⁵
14
DNC
13
DNC
GND
C1
4.7uF
C2
0.1uF
Figure 1. Typical Si7005 Application Circuit for Battery-Powered Applications
Rev 0.4 1/15
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AN764