AN4467 datasheet(6/33 Pages) STMICROELECTRONICS

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Power supplies

AN4467

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DocID026156 Rev 2

Power supplies

1.1

Introduction

The chip requires power supply on different power pins:

•

VDD= 1.65 to 3.6 V: external power supply for I/Os and the internal regulator. Provided

externally through VDD pins. For VDD below 1.8 V see Section 1.3.3: Brownout reset

(BOR)

•

VDDA = VDD: external analog power supply for ADC/DAC, Comparators, Reset blocks,

RCs and PLL. The minimum voltage to be applied to VDDA is 1.8 V when the DAC is

used.The VDDA voltage level must always be equal to VDD, a maximum difference of

300 mV between VDD and VDDA can be tolerated during power-up and normal

operation.

•

VLCD= 2.5 to 3.6 V when the LCD controller is powered externally. When the LCD is

powered internally from the voltage generated by the embedded step-up converter,

VLCD pin must be connected to a capacitor. If the LCD is not used at all, this pin should

be connected to VDDA.

•

VDD_USB = 3.0 to 3.6 V, VDD_USB is a dedicated independent USB power supply for

USB transceivers. The minimum value of 3.0 V guarantees the USB signal voltage

level. When USB is not used the application must supply VDD_USB = 1.65 to 3.6 V.

Digital power voltage (VCORE) is provided with an embedded linear voltage regulator with

three different programmable ranges from 1.2 to 1.8 V.

To be fully functional at full speed, the device requires a 1.71 to 3.6 V operating voltage

supply (VDD), making possible to reach the digital power voltage VCORE close to 1.8 V

(product voltage range 1).

Product voltage range 2 (VCORE = 1.5 V) and 3 (VCORE = 1.2 V) can be selected when the

VDD operates from 1.65 to 3.6 V. Therefore, frequency is limited to 16 MHz and 4.2 MHz,

respectively.

When the DAC and brownout reset (BOR) are not used, the device can operate at power

voltages below 1.8 V, down to 1.65 V.

AN4467 Datasheet(PDF) 6 Page - STMicroelectronics