Si3220/Si3225
VCC
VDD
Si3220/
Si3225
Polarized
relay
IDRV
RRDa/b
TRD1a/b
TRD2a/b
Q1
RDRV
Figure 29. Driving Relays with VCC > VDD
The maximum allowable R
value can be calculated with the following equation:
DRV
(VDD,MIN – 0.6 V)(RRELAY)(βQ1,MIN
)
------------------------------------------------------------------------------------------------
– RSOURCE
MaxRDRV
=
V
CC,MAX – 0.3 V
Where βQ1,MIN ~ 30 for a 2N2222.
Table 31. Recommended RDRV Values
ProSLIC V
Relay V
Relay R
Maximum R
DRV
Recommended 5% Value
DD
CC
COIL
3.3 V ±5%
5 V ±5%
3.3 V ±5%
5 V ±5%
64 Ω
Not Required
Not Required
2718 Ω
—
178 Ω
—
3.3 V ±5%
3.3 V ±5%
3.3 V ±5%
3.3 V ±5%
5 V ±5%
5 V ±5%
178 Ω
2.7 kΩ
5.6 kΩ
8.2 kΩ
11 kΩ
9.1 kΩ
13 kΩ
18 kΩ
12 V ±10%
24 V ±10%
48 V ±10%
12 V ±10%
24 V ±10%
48 V ±10%
1028 Ω
2880 Ω
7680 Ω
1028 Ω
2880 Ω
7680 Ω
6037 Ω
8364 Ω
11092 Ω
9910 Ω
5 V ±5%
13727 Ω
18202 Ω
5 V ±5%
54
Rev. 1.0
SILICONIMAGE [ Silicon image ]
