TIOS101 Datasheet, PDF (18/26 Pages) Texas Instruments – Digital Sensor Output Drivers with Integrated Surge Protection

TIOS101
SLLSEV6 – JULY 2017
www.ti.com
9.2.2 Detailed Design Procedure
9.2.2.1 Maximum Junction Temperature Check
For a 200 mA current limit:
• The maximum driver output current limit, I_O(LIM) = 250 mA (allowed for current limit tolerance).
• The maximum voltage drop across the high-side switch is given with V_DS(ON) = 1.75 V.
This causes a power consumption of:
2&₁₂ = 8_&5(10) T +_1(.+/) = 1.758 T 250 I# = 437.5 I9
(1)
For a 5 mA LDO current output,
2&_.&1 = k8_.+ F 8_{8%%_176} o x +_{8%%_176} = :30 F 5;V x 5 mA = 125 mW
(2)
Total power dissipation,
2& = 2&₁₂ + 2&_.&1 = 437.5 I9 + 125 I9 = 562.5 I9
(3)
Multiply this value with the Junction-to-ambient thermal resistance of θ_JA = 68.1°C/W (taken from the Thermal
Information table) to receive the difference between junction temperature, T_J, and ambient temperature, T_A:
¿6 = 6_, F 6_# = 2& x E_,# = 562.5 I9 T 68.1°%/9 = 38.3°%
(4)
Add this value to the maximum ambient temperature of T_A = 105°C to receive the final junction temperature:
6_,FI=T = 6_#FI=T + ¿6 = 105°% + 38.3°% = 143.3°%
(5)
As long as T_J-max is below the recommended maximum value of 150°C, no thermal shutdown will occur.
However, thermal warning may occur as the junction temperature is greater than T_WRN.
Note that the modeling of the complete system may be necessary to predict junction temperature in smaller
PCBs and/or enclosures without air flow.
9.2.2.2 Driving Capacitive Loads
These devices are capable of driving capacitive loads on the OUT output. Assuming a pure capacitive load
without series/parallel resistance, the maximum capacitance that can be charged without triggering current fault
can be calculated as:
C_LOAD
[I_{O LIM} x t_SC ]
V _VCC
(6)
Higher capacitive loads can be driven if a series resistor is connected between the OUT and the load. Capacitive
loads can be connected to VCC and GND.
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