Rainbow-electronics ATmega8HVD Manuel d'utilisateur télécharger pdf (Page 100)

100

8052B–AVR–09/08

ATmega4HVD/8HVD

19. Voltage Regulator

19.1 Features

• Linear regulation giving a fixed output voltage (VREG) of 2.2V for VFET > V

FORCE

• Output voltage forced as close as possible to VFET for VFET ≤ V

FORCE

to facilitate low voltage

operation.

• Regulator Short-circuit Detection (RSCD), disconnecting VFET from VREG if VFET drops below

the Regulator Short-Circuit Detection voltage (V

RSCD

)

• RSCD enabling/disabling in software

19.2 Overview

The Voltage Regulator is a linear regulator that nominally provides a fixed output voltage

(VREG). However, to facilitate efficient low-voltage operation with minimum voltage drop

caused by the regulator, voltage regulation is automatically switched off when VFET is below

FORCE

(see ”Electrical Characteristics” on page 142). VREG as a function VFET and regulator

is illustrated in Figure 19-1. A discontinuity in VREG can be observed as the point where the

regulator switches from linear mode to FORCE mode, as VREG is being forced as close as

possible to VFET. The voltage drop from VFET to VREG in this mode depends on the load

current on VREG.

Figure 19-1. VREG/VCC as function of VFET

The Voltage regulator mode depending on operating conditions and SW settings, are summa-

rized in Table 19-1.

Table 19-1.

VFET Voltage Regular Short-circuit Detection Regular mode

VFET > V

FORCE

Enabled/Disabled Normal Linear Regulation

VFET< V

FORCE

Enabled Battery Pack Short mode

VFET < V

FORCE

Disabled Force mode

2.2V

BLOT, NORMAL

VREG

LINEAR

Regulator Mode

FORCE OFF

VFET

FORCE

ENABLED

Short-circuit Detection

DISABLED

1 2 ... 95 96 97 98 99 100 101 102 103 104 105 ... 167 168

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Rainbow-electronics ATmega8HVD Manuel d'utilisateur Page 100

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