71M6541DSLASHFSLASHG datasheet(15/166 Pages) MAXIM

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

Rev 5

The performance of the IAP-IAN pins can be enhanced by enabling a pre-amplifier with a fixed gain of 8,

using the I/O RAM control bit PRE_E (I/O RAM 0x2704[5]). When PRE_E = 1, IAP-IAN become the inputs

to the 8x pre-amplifier, and the output of this amplifier is supplied to the multiplexer. The 8x amplification

is useful when current sensors with low sensitivity, such as shunt resistors, are used. With PRE_E set, the

IAP-IAN input signal amplitude is restricted to 31.25 mV peak.

For the 71M654x application utilizing two shunt resistor sensors (Figure 3), the IAP-IAN pins are configured

for differential mode to interface to a local shunt by setting the DIFFA_E control bit. Meanwhile, the IBP-IBN

pins are re-configured as digital balanced pair to communicate with a 71M6x01 Isolated Sensor interface by

setting the RMT_E control bit (I/O RAM 0x2709[3]). The 71M6x01 communicates with the 71M654x using a

bi-directional digital data stream through an isolating low-cost pulse transformer. The 71M654x also supplies

power to the 71M6x01 through the isolating transformer. This type of interface is further described at the

end of this chapter (see 2.2.8 71M6x01 Isolated Sensor Interface (Remote Sensor Interface)).

For use with Current Transformers (CTs), as shown in Figure 2, the RMT_E control bit is reset, so that the

IBP-IBN pins are configured as local analog inputs. The IAP-IAN pins cannot be configured as a remote

sensor interface.

2.2.2

Input Multiplexer

When operating with local sensors, the input multiplexer sequentially applies the input signals from the analog

input pins to the input of the ADC (see Figure 2 and Figure 4). One complete sampling sequence is called a

multiplexer frame. The multiplexer of the 71M6541D/F can select up to three input signals (IAP-IAN, VA, and

IBP-IBN) per multiplexer frame as controlled by the I/O RAM control field MUX_DIV[3:0] (I/O RAM

0x2100[7:4]) (see Figure 6). The multiplexer of the 71M6542F/G adds the VB signal to achieve a total

of four inputs (see Figure 7). The multiplexer always starts at state 1 and proceeds until as many

states as determined by MUX_DIV[3:0] have been converted.

The 71M6541D/F/G and 71M6542F/G each require a unique CE code that is written for the specific

application. Moreover, each CE code requires specific AFE and MUX settings in order to function

properly. Table 1 provides the CE code and settings corresponding to the local sensor configurations

shown in Figure 2 and Figure 4. Table 2 provides the CE code and settings corresponding to the

local/remote sensor configuration utilizing the 71M6x01 as shown in Figure 3 and Figure 5.

Table 1. Required CE Code and Settings for Local Sensors

I/O RAM

Mnemonic

I/O RAM

Location

71M6541D/F/G

(hex)

71M6542F/G

(hex)

Eq. 0 or 1

Eq. 2

FIR_LEN[1:0]

210C[2:1]

ADC_DIV

2200[5]

PLL_FAST

2200[4]

MUX_DIV[3:0]

2100[7:4]

MUX0_SEL[3:0]

2105[3:0]

MUX1_SEL[3:0]

2105[7:4]

MUX2_SEL[3:0]

2104[3:0]

MUX3_SEL[3:0]

2104[7:4]

RMT_E

2709[3]

DIFFA_E

210C[4]

DIFFB_E

210C[5]

EQU[2:0]

2106[7:5]

0 or 1

CE Code

CE41A01

CE41A04

Equations

0 or 1

Current Sensor Types

1 Shunt and 1 CT

2 CTs

1 Shunt and 1 CT

2 CTs

1 Shunt and 1 CT

2 CTs

Applicable Figure

Figure 2

Figure 4

Notes:

1. MUX_DIV[3:0] must be set to 0 while writing the other RAM locations in this table.

Maxim updates the CE code periodically. Contact your local Maxim representative to obtain the latest CE code and

the associated settings. The configuration presented in this table is set by the MPU demonstration code during

initialization.

71M6541D/F/G Datasheet(PDF) 15 Page - Maxim Integrated Products

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