SLVA343A Datasheet, PDF (5/8 Pages) Texas Instruments – Medium Integrated Power Solution Using a Dual DC/DC Converter and an LDO

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Features
Proper sequencing is ensured in the design with the use of a NPN transistor and a N-channel MOSFET.
As required, Core 1.2 V at 600 mA comes first , which in turn pulls up the gate of a N-channel MOSFET to
3.3 V with the use of a NPN transistor. Then 1.2 V + VRTC at 251 mA comes up. This 1.2 V further
enables the DCDC1 and sequentially 1.8 V comes up, which again enables an LDO to give 3.3 V at 115
mA.
(1) Use three such LDOs to power up DVDDA, DVDDB, and DVDDC. (It can be either 1.8 V or 3.3 V.)
(2) Rx = 0.499 MΩ, Ry = 1 MΩ for Vout = 1.8 V
(3) Rx = 1.8 MΩ, Ry = 1 MΩ for Vout = 3.3 V
(4) For proper sequencing of output, enable of the LDOs are fed either from a 1.2-V output from TPS62420
DCDC2 if DVDDX is 1.8 V or from a 1.8-V output from TPS62420 DCDC1 if DVDDX is 3.3 V.
Figure 2. Optional Circuit for DVDD_A, DVDD_B and DVDD_C
SLVA343A – June 2009 – Revised May 2010
Medium Integrated Power Solution Using a Dual DC/DC Converter and an LDO
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