TLE7242-2G Datasheet, PDF (8/50 Pages) Infineon Technologies AG – 4 Channel Fixed Frequency Constant Current Control IC

TLE7242-2G
Overview
OUTx = High
Set Point change > Threshold
New Set Point > Old Set Point
Measured Current > New Set Point
OUTx = Low
Start of PWM period
Reset
Steady-
State
Mode
next
ADC value
CALC
DC
OUTx := LOW
Controller := stop
Set point change > Threshold
New Set Point < Old Set Point
OUTx = Low
INT
PRELOAD
OUTx := LOW
Controller := stop
LEAVE
HYST MODE
OUTx := LOW
Controller := stop
Measured Current < New
Set Point
Measured Current > New
Set Point
Start of PWM period
Measured Current < New Set Point
OUTx = High
Figure 5 Transient Mode State Diagram
A typical current waveform during transient mode operation is shown in Figure 6. Starting from a set point I, the
new set point II is accepted a short time after the rising edge on CS_B. The OUTx pin remains high until the
measured load current has reached the new set point. The OUTx pin is then toggled on and off to maintain the
load current near the new set point until the next PWM period begins. The device will then switch back to steady
state control and the OUTx pin will be controlled by the control loop shown in Figure 3.
During the transition from transient mode operation to steady state operation, the integrator is pre-loaded with a
SPI programmable value. This value should be chosen to give an initial PWM duty cycle approximately equal to
the duty cycle required to regulate the load current at the new set point.
i_L
setpoint ΙΙ
Steady State
Mode Begins
Transient Mode
Begins
setpoint Ι
t
PWM
setpoint ΙΙ accepted
SPI CS_B
Figure 6 Transient Mode Timing Diagram
Data Sheet
8
Rev. 1.0, 2008-07-09