TH8061 Datasheet, PDF (24/36 Pages) Melexis Microelectronic Systems – Voltage Regulator with integrated LIN Transceiver

TH8061
Voltage Regulator with integrated LIN Transceiver
Load Capacity on VCC C_L
The regulator is stabilized by the output capacitor C_L. The TH8061 requires a minimum of 4.7µF capacity
connected to the 5V output to insure stability. This capacitor should maintain its ESR in the stable region of
the ESR curve (See Figure 24) over the full operating temperature range of the application. The capacity
value and the ESR of a capacitor changes with temperature. The minimal capacity value must be kept within
the whole operating temperature range.
100
10
1
0,1
0,01
0
10
20
30
40
50
load current [mA]
Figure 24 - ESR Curves for 6.8µF ≤ C_L ≤ 100µF and Frequency of 100kHz
The value and type of the output capacitor can be selected using the diagram shown in Figure 24.
Capacity Value
The capacity value of an electrolytic capacitor is dependence from the voltage, temperature and the
frequency. The temperature coefficient of the capacity value is positive, that means that the value increases
with increasing of the temperature. The capacity value decreases with increasing of the frequency. This
behavior of a capacitor can cause that at T_A=-40°C the capacity value falls below the minimum required
capacity for the regulator. In this case the regulator becomes instable, which means the regulator starts
oscillation. The nominal value of the capacitor at T_A=25°C have to be chosen with enough margin under
consideration of the capacitor specification. The instable behavior will be amplified because of the
decreasing of the capacity with this oscillation.
ESR
The equivalent serial resistance is the resistor part of the equivalent circuit diagram of a capacitor. The ESR
value is dependent from the temperature and frequency. Normally the specified ESR values for a capacitor is
valid at a temperature of T_A=25°C and a frequency of f=100kHz.
The temperature coefficient is negative, which means with increasing of the temperature the ESR value
decreases. In the choice of the capacity has to be taken into account that the ESR can decrease at T_A=-40°C
dramatically that the valid operating area can be left, which causes that the regulator will be instable.
TH8061 – Datasheet
3901008061
Page 24 of 36
June 2004
Rev 007