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Principle of Operation
In addition to the REFGENREQ, a second reference request signal, REFBGREQ is available. The
REFBGREQ signal represents a logical OR of requests coming from the various modules that require the
bandgap reference line. Once the REFBGREQ is asserted, the bandgap, along with its bias circuitry and
local buffer, is enabled if it is not already enabled by a prior request.
The REFMODEREQ request signal is available that configures the bandgap and its bias circuitry to
operate in a sampled or static mode of operation. The REFMODEREQ signal basically represents a
logical AND of individual requests coming from the various analog modules. In reality, a REFMODEREQ
occurs only if a module's REFGENREQ or REFBGQ is also asserted, otherwise it is a do not care. When
REFMODEREQ = 1, the bandgap operates in sampled mode. When a module asserts its corresponding
REFMODEREQ signal, it is requesting that the bandgap operate in sampled mode. Because
REMODEREQ is a logical AND of all individual requests, any modules requesting static mode cause the
bandgap to operate in static mode. The BGMODE bit can be used as an indicator of static or sampled
mode of operation.
15.2.3.1 REFBGACT, REFGENACT, REFGENBUSY
Any module that is using the variable reference line causes REFGENACT to be set inside the REFCTL
register. This bit is read only and indicates to the user that the REFGEN is active or off. Similarly, the
REFBGACT is active any time one or more modules is actively utilizing the bandgap reference line and
indicates to the user that the REFBG is active or off.
The REFGENBUSY signal, when asserted, indicates that a module is using the reference and cannot
have any of it settings changed. For example, during an active ADC10_B conversion, the reference
voltage level should not be changed. REFGENBUSY is asserted when there is an active ADC10_B
conversion (ENC = 1). REFGENBUSY write protects the REFCTL register when it is asserted. This
prevents the reference from being disabled or its level changed during any active conversion.
15.2.3.2 ADC10_B
For devices that contain an ADC10_B module, if the ADC is not sampling or converting but the REFON bit
is set the REF module remains on.
430
REF Module
SLAU272C – May 2011 – Revised November 2013
Copyright © 2011–2013, Texas Instruments Incorporated