pc87591l-n05 National Semiconductor Corporation, pc87591l-n05 Datasheet - Page 166

• Manufacturer Part Number: pc87591l-n05
• Description: Lpc Mobile Embedded Controller
• Manufacturer: National Semiconductor Corporation

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4.0 Embedded Controller Modules
4.11 ANALOG TO DIGITAL CONVERTER (ADC)
The Analog to Digital Converter (ADC) monitors various voltages in the system and reports their values to the core.
The ADC can measure, with 8-bit resolution, up to 10 external voltage inputs and four internal voltage sources. The internal
voltage sources measure the V
voltage and undervoltage detection. The external voltage inputs support thermistor-based temperature measurement.
The ADC executes cycles of three voltage measurements, each assigned to a separate output channel. Each of the three
voltage channels measures one selected voltage input during the cycle.
4.11.1 Features
4.11.2 Functional Description
Inputs. The ADC has 16 inputs (AI0-13, AI15, AI16) divided in three groups:
Analog Multiplexer. A 16 to 1 analog multiplexer selects one of the inputs for measurement by connecting it to the A/D con-
verter. Switching between inputs at different voltage levels requires delaying the conversion start until the input voltage to
the A/D converter has settled to the desired accuracy.
A/D Converter. The
version is either an 8-bit, unsigned integer digital value (0 to 255) for voltage inputs.
A high-precision internal reference generator sets the full-scale voltage value (V
ADC Cycle. The ADC has three output “channels” for voltage measurement. The voltage measurement channels are not
related to specific inputs. They hold the input select control data for the next measurement and contain a buffer in which the
conversion result is stored.
An ADC cycle includes measurements of all three channels and a calibration operation. The first measurement is of the cal-
ibration measurement and the three voltage channels in ascending order, each for the specific input number contained in its
control register. The ADC waits for a programmable delay between the selection of an input and the A/D conversion start
that is necessary for A/D input settling to the required accuracy.
At the end of each A/D conversion, the result is stored in the corresponding buffer and a Data Valid (DATVAL) flag is set.
At the end of the ADC cycle, a flag is set indicating that all the channels contain new data. If enabled, an interrupt request
is sent to the core.
• Voltage measurement
• Internal high-precision reference
• Digital reading output channels
• Sampling sequence and timing
• Polling- or interrupt-driven interface
• Power consumption
• External Voltage (AI0-9). These are either temperature-dependent voltage generated by using a Negative/Positive
• Internal Voltage (AI10-13). These are internally connected to the supply voltages of the device (V
— Ten external voltage inputs and four internal power supply inputs
— 8-bit resolution
— 0V to 2.97V input voltage range
— High-impedance, ground-referenced inputs
— Enables thermistor-based temperature measurement
— Three voltage buffers
— Input selection for each voltage channel
— Three voltage measurement within 100 ms
— Cyclic measurement of the three output channels
— Separate enable for each channel
— Programmable conversion-start delay to guarantee input settling time
— Zero current when disabled
— Low operating current
Temperature Coefficient (NTC/PTC) thermistor in a resistive divider, or general-purpose, positive DC voltage sources.
V
the current drain, is not divided.
BAT
). Voltages higher than the full-scale voltage (V
, high-resolution A/D converter receives the selected input and converts it. The result of the con-
DD
, V
CC
, AV
CC
and V
(Continued)
BAT
FS
supplies. V
) are divided by 2, except for V
166
DD
, V
CC
and AV
FS
) of the A/D converter.
CC
are divided by 2 to allow both over-
BAT
which, in order to minimize
DD
, V
CC
, AV
CC
Revision 1.2
and