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TDA3668 Folha de dados(PDF) 7 Page - NXP Semiconductors |
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TDA3668 Folha de dados(HTML) 7 Page - NXP Semiconductors |
7 / 16 page 2000 Feb 01 7 Philips Semiconductors Preliminary specification Very low dropout voltage/quiescent current 5 V regulator with overvoltage switch off TDA3668AT EXAMPLE 1 The regulator is stabilized with an electrolytic capacitor of 68 µF (ESR = 0.5 Ω). At Tamb = −40 °C, the capacitor value is decreased to 22 µF and the ESR is increased to 3.5 Ω. The regulator will remain stable at a temperature of Tamb = −40 °C. EXAMPLE 2 The regulator is stabilized with an electrolytic capacitor of 10 µF (ESR = 3.3 Ω). At Tamb = −40 °C, the capacitor value is decreased to 3 µF and the ESR is increased to 20 Ω. The regulator will remain stable at a temperature of Tamb = −40 °C. EXAMPLE 3 The regulator is stabilized with a 100 nF MKT capacitor connected to the output. Full stability is guaranteed when the output current is larger then 200 µA. Because the thermal influence on this capacitor value is almost zero, the regulator will remain stable at a temperature of Tamb = −40 °C. EXAMPLE 4 The regulator is stabilized with a 100 nF capacitor in parallel with an electrolytic capacitor of 10 µF connected to the output. The regulator is now stable under all conditions and independent of: • The ESR of the electrolytic capacitor • The value of the electrolytic capacitor • The output current. Application circuits The maximum output current of the regulator equals: When Tamb =21 °C and VP = 14 V the maximum output current equals 140 mA. For successful operation of the IC (maximum output current capability) special attention has to be given to the PCB ground plane required as heatsink, the thermal capacity of the heatsink and its ability to transfer heat to the external environment. For the SO8 package it is possible to reduce the total thermal resistance from 125 to 50 K/W. APPLICATION CIRCUIT WITH BACKUP FUNCTION Sometimes a backup function is needed to supply, for example, a microcontroller for a short period of time when the supply voltage spikes to 0 V (or even −1 V). This function can easily be built with the TDA3668AT by using an output capacitor with a large value. When the supply voltage is 0 V (or −1 V), only a small current will flow into pin REG from this output capacitor (a few µA). The application circuit is given in Fig.7. I REG max () 150 T amb – R th(j-a) V P V REG – () × ------------------------------------------------------- = 150 T amb – 100 V P 5 – () × ------------------------------------- (mA) = handbook, halfpage MGS592 VP 81 2, 3, 6, 7 C2(2) TDA3668AT C1(1) 1 µF VREG = 5 V Fig.7 Application circuit with backup function. (1) C1 is optional (to minimize supply noise only). (2) C2 ≤ 4700 µF. |
Nº de peça semelhante - TDA3668 |
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Descrição semelhante - TDA3668 |
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