TLE4247 Datasheet, PDF (8/14 Pages) Infineon Technologies AG – Constant Current Relay Driver

TLE4247
Operation Modes
5
Operation Modes
5.1
Description
The TLE4247 provides two different operation modes: For relay activation, the IC pass element works as an
activated switch with lowest dropout voltage V_DR (see Figure 3 a). After the activation time period t_Actv has elapsed,
the IC switches to hold mode regulating the relay coil current to constant values (see Figure 3 b).
During commutation, the relay coil current flows from the IC input “IN” to “S” into the relay freewheeling resistor.
A zener structure prevents the IC from overvoltage by limiting the input voltage transient to V_Z.
The relay activation time period t_Actv is generated by charging the external capacitor C_D at pin D with a constant
current. This time period starts once the IC supply voltage exceeds V_S,Start. In case the IC supply voltage V_S falls
below the threshold V_S,Hold-Actv, the IC changes to active mode allowing maximum relay current flow at low vehicle
battery voltage.
At low supply voltage, the IC switches to “Low Voltage Mode” with lowest current consumption. As in activation
mode, the IC is working as a switch with lowest dropout voltage.
In order to prevent the IC from excessive power dissipation at high supply voltage, the IC is working as a switch
(High Voltage Mode). A transition to Hold Mode during this mode is not possible.
An overtemperature protection circuit prevents the IC from immediate destruction under fault conditions by
reducing the output current. A thermal balance below 200 °C junction temperature will be established. Please note
that a junction temperature above 150 °C is outside the maximum ratings and reduces the IC lifetime.
6
,1
%LDVLQJ
%DQGJDS
)ZG
&RQWURO
'ULYHU
9_'5
9₌
6
,1
%LDVLQJ
%DQGJDS
)ZG
&RQWURO
,_,1+ROG
'ULYHU
9₌
' _'HOD\
&*1'
' _'HOD\
&*1'
D$FWLYDWLRQ0RGH
+LJK9ROWDJH0RGH
/RZ9ROWDJH0RGH
Figure 3 Operation as switch or current source
E+ROG0RGH
%ORFN'LDJUDPB0RGHVVYJ
Datasheet
8
Rev. 1.01, 2010-05-04