TLE7469_08 Datasheet, PDF (13/21 Pages) Infineon Technologies AG – Dual Low Drop Voltage Regulator Ultra low quiescent current consumption < 55 μA

TLE 7469
Since the regulator output current roughly rises linearly with time the discharge of the
capacitor can be calculated as follows:
dVC_B = dI_Q*dt/C_B
The drop across the ESR calculates as:
dV_ESR = dI*ESR
To prevent a reset the following relationship must be fullfilled:
dV_C + dV_ESR < V_RH2 = 130mV
Example: Assuming a load current step of dI_Q = 50mA, a blocking capacitor of C_Q =
22µF and a typical regulator reaction time under normal operating conditions of dt ~
25µs and for special dynamic load conditions, such as load step from very low base
load, a reaction time of dt ~ 75µs.
dV_C = dI_Q*dt/C_B = 50mA * 25µs/22µF = 54mV
So for the ESR we can allow
dV_ESR = V_RH2 - dV_C = 130mV - 54mV = 76mV
The permissible ESR becomes:
ESR = dV_ESR / dI_Q = 76mV/50mA = 1.52Ohm
During design-in of the TLE7469 product family, special care needs to be taken with
regards to the regulators reaction time to sudden load current changes starting from very
low pre-load as well as cyclic load changes. The application note “TLE7x Voltage
Regulators - Application Note about Transient Response at ultra low quiescent current
Voltage Regulators” (see 3_cip05405.pdf) gives important hints for successful design-in
of the Voltage Regulators of the TLE7x family.
As a dual regulator the TLE 7469 for correct operation should be always supplied at both
input pins I1 and I2 out of one voltage supply. The dual voltage regulator with both inputs
accessible, offers the possibility to reduce the power dissipation in the package. This can
be achived by two different input voltages or a Drop Resistor* R_Vi (see Figure 3) at the
input pin I2 for the 2.6V output. If one of this options is chosen,care should be taken, to
apply the device as descibed under “Table 3: Operating Range”.
The reset output RO features an integrated pull-up resistor. Thus it can be directly
coupled to the microcontroller reset input.
Data Sheet
13
Rev. 1.6, 2008-01-22