71M6511 Maxim, 71M6511 Datasheet - Page 10

• Manufacturer Part Number: 71M6511
• Description: The 71M6511 and 71M6511H are highly integrated SoCs with an MPU core, RTC, flash, and LCD driver
• Manufacturer: Maxim

It is assumed that an offset voltage Voff appears at the positive amplifier input. With all switches, as controlled by CROSS in
the “A” position, the output voltage is:
With all switches set to the “B” position by applying the inverted CROSS signal, the output voltage is:
Thus, when CROSS is toggled, e.g. after each multiplexer cycle, the offset will alternately appear on the output as positive and
negative, which results in the offset effectively being eliminated, regardless of its polarity or magnitude.
The Functional Description Section contains a chapter with a detailed description on controlling the CHOP_ENA register.
Temperature Sensor
The 71M6511/6511H includes an on-chip temperature sensor implemented as a bandgap reference. It is used to determine
the die temperature The MPU may request an alternate multiplexer cycle containing the temperature sensor output by
asserting MUX_ALT.
The primary use of the temperature data is to determine the magnitude of compensation required to offset the thermal drift in
the system (see section titled “Temperature Compensation”).
The zero reference for the temperature sensor is VBIAS.
Functional Description
The AFE functions as a data acquisition system, controlled by the MPU. The main signals (IA, VA, IB) are sampled and the
ADC counts obtained are stored in CE RAM where they can be accessed by the CE and, if necessary, by the MPU. Alternate
multiplexer cycles are initiated less frequently by the MPU to gather access to the slow temperature signal.
Page: 10 of 98
A Maxim Integrated Products Brand
Voutp – Voutn = G (Vinp + Voff – Vinn) = G (Vinp – Vinn) + G Voff
Voutn – Voutp = G (Vinn – Vinp + Voff) = G (Vinn – Vinp) + G Voff, or
Voutp – Voutn = G (Vinp – Vinn) - G Voff
VA
IA
IB
TEMP
V
V
inp
inn
CROSS
EQU
MUX_ALT
MUX_DIV
CTRL
Figure 2: General Topology of a Chopped Amplifier
MUX
MUX
MUX
© 2005–2010 Teridian Semiconductor Corporation
B
A
B
A
CK32
CHOP_EN
VREF_DIS
VREF
VBIAS
+
-
VREF VBIAS
G
V3P3A
Single-Phase Energy Meter IC
+
VREF
-
A
B
B
A
71M6511/71M6511H
CONVERTER
∆Σ ADC
DATA SHEET
V
V
FIR_LEN
outp
outn
FILTER
FIR
NOVEMBER 2010
V2.7