OutputClamp.emf

OUT

V

DS

GND

L,

Data Sheet

13

Rev. 1.0, 2007-12-18

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

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.

Figure 5

Output Clamp Implementation

Maximum Load Inductance

CS

t

SwitchOn.emf

t

20%

80%

SPI: ON

SPI: OFF

During demagnetization of inductive loads, energy has to be dissipated in the SPIDER - TLE7232GS. This energy

can be calculated with following equation:

(1)

The equation simplifies under the assumption of

R

(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

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.

–

DS(CL)

---------------------------------- ln

⋅

1

⋅

–

DS(CL)

----------------------------------

–





+

L

------

⋅⋅

=

E

1

2

---

2

1

–

DS(CL)

----------------------------------

–





⋅

=