tle8242 Infineon Technologies Corporation, tle8242 Datasheet - Page 7

• Manufacturer Part Number: tle8242
• Description: 8 Channel Fixed Frequency Constant Current Control With Current Profile Detection
• Manufacturer: Infineon Technologies Corporation

divider, N, can be set to any value between 79 and 2
PWM mode, the value M can also be set to 512. The equation for calculating the PWM frequency is:
In constant current mode, the value of M is the number of A/D samples within one PWM period. Setting the SAM
bit in SPI Message #8 to a “1” will cause the ADC samples immediately following a change in the state of the OUTx
pin to be discarded. If the SAM bit is set to ‘0’, all M A/D samples are used in the average calculation.
The 11 bit Current Set Point is programmed via the SPI message #10. The equation for calculating the current
setpoint is:
The Proportional coefficient (KP) and the Integral coefficient (KI) of the control loop are programmed in SPI
message #9. The KP and KI values should be set to values that result in the desired transient response of the
control loop. The duty cycle of the OUTx pin can be calculated from the difference equations:
where error is the difference between the commanded average current and measured average current in units of
Amps.
where k indicates the integer number of PWM periods that have elapsed since current regulation was initiated.
Data Sheet
DutyCycle
INT
(
k
)
Current
=
KI
( )
k
setpoint
∗
=
. 1
Rsense
KP
28
[
mA
F
∗
∗
]
PWM
N
. 1
=
Rsense
setpoint(1
28
*
14
error
=
-1 and the divider M can be set to 32, 64, or 128. In direct
∗
7
2
N
M
11
F
*
CLK
1bit)
(
∗
k
error
N
−
∗
1
)
R
+
SENSE
(
k
INT
320
−
[
ohm
1
)
(
+
k
]
INT
−
) 1
(
k
Rev. 1.0, 2009-02-25
)
TLE8242
Overview