71M6541DSLASHFSLASHG datasheet(14/166 Pages) MAXIM

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71M6541D/F/G and 71M6542F/G Data Sheet

Rev 5

Figure 5 shows the 71M6542F/G multiplexer interface with one local and one remote resistive shunt

sensor. As seen in Figure 5, when a remote isolated shunt sensor is connected via the 71M6x01, the

samples associated with this current channel are not routed to the multiplexer, and are instead

transferred digitally to the 71M6542F/G via the digital isolation interface and are directly stored in CE

RAM.

See Figure 6 for the multiplexer timing sequence corresponding to Figure 5. See Figure 38 for the meter

configurations corresponding to Figure 5.

DS ADC

CONVERTER

VREF

MUX

VREF

VADC

FIR

IBP

VADC9 (VB)

IAP

VADC10 (VA)

IAN

IBN

71M6542F

CE RAM

71M6x01

INP

INN

Remote

Shunt

Digital

Isolation

Interface

Local

Shunt

11/5/2010

Figure 5. 71M6542F/G AFE Block Diagram with 71M6x01

2.2.1

Signal Input Pins

The 71M6541D/F/G features five ADC inputs. The 71M6542F/G features six ADC inputs.

IAP-IAN and IBP-IBN are intended for use as current sensor inputs. These four current sensor inputs can be

configured as two single-ended inputs, or can be paired to form two differential inputs. For best

performance, it is recommended to configure the current sensor inputs as differential inputs (i.e., IAP-IAN

and IBP-IBN). The first differential input (IAP-IAN) features a pre-amplifier with a selectable gain of 1 or 8,

and is intended for direct connection to a shunt resistor sensor, and can also be used with a Current

Transformer (CT). The remaining differential pair (i.e., IBP-IBN) may be used with CTs, or may be enabled

to interface to a remote 71M6x01 isolated current sensor providing isolation for a shunt resistor sensor using

a low cost pulse transformer.

The remaining input in the 71M6541D/F (VA) is single-ended, and is intended for sensing the line voltage in

a single-phase meter application using Equation 0 or 1 (see 2.3.4 Meter Equations on page 25). The

71M6542F/G features an additional single-ended voltage sensing input (VB) to support bi-phase

applications using Equation 2. These single-ended inputs are referenced to the V3P3A pin.

All analog signal input pins measure voltage. In the case of shunt current sensors, currents are sensed as a

voltage drop in the shunt resistor sensor. Referring to Figure 3, shunt sensors can be connected directly to

the 71M654x (referred to as a ‘local’ shunt sensor) or connected via an isolated 71M6x01 (referred to as a

‘remote’ shunt sensor). In the case of Current Transformers (CT), the current is measured as a voltage

across a burden resistor that is connected to the secondary winding of the CT. Meanwhile, line voltages are

sensed through resistive voltage dividers. The VA and VB pins (VB is available in the 71M6542F/G only)

are single-ended and their common return is the V3P3A pin.

Pins IAP-IAN can be programmed individually to be differential or single-ended as determined by the

DIFFA_E (I/O RAM 0x210C[4]) control bit. However, for most applications, IAP-IAN are configured as a

differential input to work with a shunt or CT directly interfaced to the IAP-IAN differential input with the

appropriate external signal conditioning components (see 4.2 Direct Connection of Sensors on page 92).

71M6541D/F/G Datasheet(PDF) 14 Page - Maxim Integrated Products

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