33888 Datasheet, PDF (29/40 Pages) Freescale Semiconductor, Inc – Quad High-Side and Octal Low-Side Switch for Automotive

TYPICAL APPLICATIONS
Figure 13. Figure 13 – MC33888 power dissipation calculator
Automotive lamps do not tolerate high voltages very well.
Tests of a few lamps indicated that failures can occur when
18V is applied for a few seconds. Consequently, PWM
switching allows to reduce the effective RMS voltage in order
to drive bulbs safety. The “Vbatt PWM” threshold determines
the transition between the fully-on and PWMing modes.
For example, to maintain the power dissipation associated
with a 13V battery at 100% duty cycle, the duty cycle would
be adjusted to (13/18)², or 52%, when the battery is at 18V.
The loads must be chosen in order to guarantee the device
normal operating condition as junction temperature from -40
to 150 °C. In case of permanent current limitation conditions,
the duration and number of activation cycles must be limited
with a dedicated MCU fault management using the fault
reporting through SPI.
SHAFFNER TESTS
The MC33888 device is protected in case of positive and
negative transients on VPWR and the output lines (HS[0:3]
and LS[4:11]) per ISO 7637-2 standard.
The following characterization has been done without
decoupling capacitors and for HS1 resistive load=2.5Ω and
HS3 resistive load=3Ω.
Table 11. Results of Fast Transient Pulses on VPWR
Pulses on VPWR
HS1 & 3 ON state
loaded
HS1 & 3 ON state
open load
Pulse 1 Ri = 10Ω
5000 occurrences
PASS: -100V
PASS : -40V,
FAIL : -50V
Pulse 2a Ri = 2Ω
5000 occurrences
Pulse 3a Ri = 50Ω
Duration 1 hour
PASS: +50V
PASS: -150V
PASS: +42V ,
FAIL: +50V
PASS: -150V
Pulse 3b Ri = 50Ω
Duration: 1 hour
PASS: +100V
PASS: +100V
Pulse 5a Ri = 2Ω
(Load dump) 50 pulses
PASS: +42V
PASS: +42V
Pulse 5b Ri = 2Ω
(Load dump) 50 pulses
PASS: +42V
PASS: +42V
HS1 & 3 OFF state
loaded
PASS: -100V
PASS: +50V
PASS: -150V
PASS: +100V
PASS: +42V
PASS: +42V
HS1 & 3 OFF state
open load
PASS : -40V,
FAIL: -50V
PASS: +50V
PASS: -150V
PASS: +100V
PASS: +42V
PASS: +42V
Analog Integrated Circuit Device Data
Freescale Semiconductor
33888
29