AN883
LOW-COST I2C LEVEL TRANSLATOR
1. Introduction
This applications note discusses a low-cost circuit for I2C level ...
AN883
LOW-COST I2C LEVEL TRANSLATOR
1. Introduction
This applications note discusses a low-cost circuit for I2C level translation. This circuit was developed for the Si701x, Si702x, and Si703x humidity sensors but will work in many applications. This circuit provides I2C level translation from a higher
voltage supply, such as 5 V, to a lower
voltage, supply such as 1.8 or 3.3 V. In addition, the optional emitter follower circuit provides a low-
voltage power supply rail from the higher 5 V supply. Note that some devices allow for higher
voltage tolerance on I2C inputs. For example, the Si7034 has a 3.3 V tolerant I2C interface, so the level translation is only required for 5 V I2C designs.
2. Circuit
The basic circuit is shown in Figure 1.
5V Optionally replace with LDO
1.8V
U3
VCC SCL SDA GND
4 3 2 1
R1 4.7K
R2 4.7K
R6 10K
R7 6.65K
D3 BAS16X
Q3 MMBT3904
R8 10K
R3 4.7K
R4 4.7K
D1 BAS40
D2
2 SCL
4 SDA
5 VSS
1 VDD
U1 Si7034
6 NC NC 3
C1 0.1uF
BAS40
Q2 MMBT3904
1.8V
R...