TYPICAL APPLICATION
INTRODUCTION
TYPICAL APPLICATION
INTRODUCTION
The 33874 can be configured in several applications. The figure below shows the 33874 in a typical lighting application.
VPWR
VDD
Voltage regulator
VPWR
VDD
VDD
VPWR
VDD
VPWR
VDD
100nF
10k
10k
10µF
100nF
NC
VDD
WAKE
HS0
HS1
HS2
I/O
FS
LOAD 0
LOAD 1
LOAD 2
10k
I/O
I/O
I/O
I/O
IN0
21W
5W
10k
10k
10k
IN1
IN2
IN3
Microcontroller
33874
10k
10k
10k
SCLK
CS
I/O
SO
SI
SCLK
CS
RST
21W
21W
5W
5W
10k
SI
SO
TEMP
CSNS
FSI
A/D
A/D
HS3
LOAD 3
GND
21W
5W
1k
R1
Automotive lamps do not tolerate high voltages very well. Tests of a few lamps indicate that failures can occur when
18V is applied for a few seconds. Consequently, PWM switching reduces the effective RMS voltage in order to drive
bulbs safety.
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 short-circuit conditions, the duration and number of activation cycles must
be limited with a dedicated MCU fault management using the fault reporting through SPI.
33874
Analog Integrated Circuit Device Data
Freescale Semiconductor
28
FREESCALE [ Freescale ]
