ST AN2202 Application note

AN2202

Application note

STR73x microcontroller power management

Introduction

This application note provides an overview of the STR73x power management features and gives some guidelines for using the low power modes to minimize the power consumption of the microcontroller.

Example software is provided with this application note for implementing and showing the various low power modes.

September 2006

Rev 2

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AN2202

Contents

1 Power supply . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

1.1 Power supply pins . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 1.2 Internal regulators . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

1.2.1 Low Power Voltage Regulator (LPVR) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

2	Clock management . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .		5
	2.1	Clock configuration & power management . . . . . . . . . . . . . . . . . . . . . . . . . . .	5
	2.2	Disabling peripherals clocks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	5
3	STR73x low power modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .		6

3.1 Low power mode characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 3.2 Guidelines for entering/exiting low power modes . . . . . . . . . . . . . . . . . . . . . . 6

3.2.1 SLOW mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 3.2.2 WFI mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 3.2.3 LPWFI mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 3.2.4 STOP mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 3.2.5 HALT mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

4	Example application . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .		. 9
	4.1	Example hardware . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	9
	4.2	Example software . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	9
	4.3	Power consumption measurements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	10

5 Revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

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AN2202

1 Power supply

1 Power supply

1.1Power supply pins

The following figure indicates the recommended configuration for the power supply pins:

Figure 1. STR73x power supply pins

5V

STR73x

VDD

AVDD

AVSS

V18

100nF

VSS

VSS

VSS

●VDD pin: is the 5V main power supply pin.

●V18 pin: must be connected to a capacitor of at least 100nF (ceramic) in order to guarantee the stability of the 1.8V supply to the core.

1.2Internal regulators

The following figure provides a schematic view of the power management block of the STR73x.

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1 Power supply

AN2202

Figure 2. Power management block

AVDD	A/D converter
AVSS
V18
VDD	Memory and I/Os
	Main Voltage Regulator	V18		Core and Peripherals
			Note*
	Low Power Voltage Regulator		V18	Peripherals active
				in LPWFI mode

Note: * Disconnected in LPWFI mode.

Main Voltage Regulator (MVR)

In normal operation, the Main Voltage Regulator (MVR) provides the 1.8V supply. The MVR can be switched off when entering a low power mode (refer to Section 3)

When the MVR is switched off, the Low Power Voltage Regulator (LPVR) can provide a power supply of about 1.8V (+/- 10%).

Note: 1 The MVR has a static power consumption of 3.97 mA typ at 25°C.

2When the MVR is switched off, The PLL is automatically disabled (PLL off) and the maximum allowed operating frequency is 2 MHz, this is due to the limitation imposed by the LPVR which is not able to generate sufficient current to operate in run mode.

1.2.1Low Power Voltage Regulator (LPVR)

The Low Power Voltage Regulator (LPVR) is used when the MCU is in low-power mode and the main voltage regulator has been switched off. It has a different design from the main voltage regulator and generates a stabilized and thermally-compensated voltage in the range of 1.8V (+/- 10%), its output current is not generally sufficient for the device to run in normal operation.

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