TLE4269_07 Datasheet, PDF (5/19 Pages) Infineon Technologies AG – 5-V Low Drop Fixed Voltage Regulator Output voltage tolerance ≤ ±2%

TLE 4269
Circuit Description
The control amplifier compares a reference voltage, made highly accurate by resistance
balancing, with a voltage proportional to the output voltage and drives the base of the
series PNP transistor via a buffer. Saturation control as a function of the load current
prevents any over-saturation of the power element.
The reset output RO is in high-state if the voltage on the delay capacitor C_D is greater or
equal V_UD. The delay capacitor C_D is charged with the current I_D for output voltages
greater than the reset threshold V_RT. If the output voltage gets lower than V_RT (‘reset
condition’) a fast discharge of the delay capacitor C_D sets in and as soon as V_D gets
lower than V_LD the reset output RO is set to low-level.
The time gap for the delay capacitor discharge is the reset reaction time t_RR.
The reset threshold V_RT can be decreased via an external voltage divider connected to
the pin RADJ. In this case the reset condition is reached if V_Q < V_RT and
V_RADJ < V_{RAQDJ, TH}. Dimensioning the voltage divider (Figure 5) according to:
V_THRES = V_RADJ,TH × (R_ADJ1 + R_ADJ2) / R_ADJ2,
(1)
the reset threshold can be decreased down to 3.5 V. If the reset-adjust-option is not
needed the RADJ-pin should be connected to GND causing the reset threshold to go to
its default value (typ. 4.65 V).
A built in comparator compares the signal of the pin SI, normally fed by a voltage divider
from the input voltage, with the reference and gives an early warning on the pin SO. It is
also possible to superwise another voltage e.g. of a second regulator, or to build a
watchdog circuit with few external components.
Application Description
The input capacitor C_I is necessary for compensating line influences. Using a resistor of
approx. 1 Ω in series with C_I, the oscillating circuit consisting of input inductivity and input
capacitance can be damped. The output capacitor C_Q is necessary for the stability of the
regulating circuit. Stability is guaranteed at values ≥ 10 µF and an ESR ≤ 10 Ω within the
operating temperature range. For small tolerances of the reset delay the spread of the
capacitance of the delay capacitor and its temperature coefficient should be noted.
Data Sheet
5
Rev. 2.4, 2007-03-20