LTC2662 datasheet(20/28 Pages) AD

20 / 28 page

LTC2662

Rev 0

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OPERATION

Due to the pre-charge behavior, the mux output becomes

valid approximately 7µs after the Mux command is given

(CS/LD rising). Residual charging transients can be fur-

ther reduced by adding capacitance to the output pins if

needed. Do not add capacitance to the MUX pin, as this

potentially increases the disturbance to the outputs during

mux switching. Up to 100pF on the MUX pin is allowable.

Toggle Operations

Some systems require that the DAC outputs switch repeti-

tively between two output levels (i.e. switching between

an ‘on’ and ‘off’ state). The LTC2662 toggle function facili-

tates these kinds of operations by providing two input

registers (A and B) per DAC channel.

Toggling between A and B is controlled by three signals.

The first of these is the toggle select command, which

acts on the data field of 5 bits, each of which controls a

single channel (see Figure 7). The second is the global

toggle command, which controls all selected channels

using the global toggle bit TGB (see Figure 8). Finally, the

TGP pin allows the use of an external clock or logic signal

to toggle the DAC outputs between A and B. The signals

from these controls are combined as shown in Figure 9.

If the toggle function is not needed, tie TGP (Pin 2) to

ground and leave the toggle select register in its power-

on reset state (cleared to zero). Input registers A then

function as the sole input registers, and registers B are

not used.

Table 4. Monitor Mux Control Codes

MUX PIN OUTPUT

NOTES:

Disabled (Hi-Z)

OUT0 Current Measurement

IOUT0 = IFS • VMUX/VREF

OUT1 Current Measurement

IOUT1 = IFS • VMUX/VREF

OUT2 Current Measurement

IOUT2 = IFS • VMUX/VREF

OUT3 Current Measurement

IOUT3 = IFS • VMUX/VREF

OUT4 Current Measurement

IOUT4 = IFS • VMUX/VREF

VCC

VREF

VREFLO

DAC Reference GND

Die Temperature, T

T = 25°C + (1.4V – VMUX)/(0.0037V/°C)

VDD0

VDD1

VDD2

VDD3

VDD4

V+

V–

GND

OUT0 Pin Voltage

OUT1 Pin Voltage

OUT2 Pin Voltage

OUT3 Pin Voltage

OUT4 Pin Voltage

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