TLE7232GS Datasheet, PDF (13/32 Pages) Infineon Technologies AG – SPI Driver for Enhanced Relay Control

SPI Driver for Enhanced Relay Control
SPIDER - TLE7232GS
Block Description and Electrical Characteristics
5.1.3 Inductive Output Clamp
When switching off inductive loads, the potential at pin OUT rises to V_DS(CL) potential, because the inductance
intends to continue driving the current. The voltage clamping is necessary to prevent destruction of the device,
see Figure 5 for details. Nevertheless, the maximum allowed load inductance is limited.
V_bat
V_DS(CL)
OUT
L,
I_D
R_L
V_DS
GND
Figure 5 Output Clamp Implementation
OutputClamp .emf
Maximum Load Inductance
During demagnetization of inductive loads, energy has to be dissipated in the SPIDER - TLE7232GS. This energy
can be calculated with following equation:
E = V_DS(CL) ⋅
V_{-----b--a--t---}–_-----V_{----D---S---(-C---L--)}
R_L
⋅
ln_1
–
---------^R-----^L---^â‹---^I---^D----------
V_bat – V_DS(CL)


+ I_D
⋅ --^L----
R_L
(1)
The equation simplifies under the assumption of R_L = 0:
E
=
1--
2
L
I_D2
⋅
¹
–
-------------^V----^b--^a---^t-----------
V_bat – V_DS(CL)


(2)
The energy, which is converted into heat, is limited by the thermal design of the component.
5.1.4 Timing Diagrams
The power transistors are switched on and off with a dedicated slope via the OUT bits of the serial peripheral
interface SPI. The switching times t_ON and t_OFF are designed equally.
CS
V_DS
80%
SPI: ON
t_ON
SPI: OFF
t_OFF
t
20%
t
SwitchOn.emf
Figure 6 Switching a Resistive Load
When the input mapping is configured accordingly, a high signal at the input pin is equivalent to a SPI ON
command.
Data Sheet
13
Rev. 1.0, 2007-12-18