MAX5590 datasheet(29/33 Pages) MAXIM

29 / 33 page

Buffered, Fast-Settling, Octal, 12/10/8-Bit,

Voltage-Output DACs

______________________________________________________________________________________

GPI, GPOL, GPOH

UPIO1 and UPIO2 can each be configured as a gener-

al-purpose input (GPI), a general-purpose output low

(GPOL), or a general-purpose output high (GPOH).

The GPI can serve to detect interrupts from µPs or micro-

controllers. The GPI has three functions:

1) Sample the signal at GPI at the time of the read

(RTP1 and RTP2).

2) Detect whether or not a falling edge has occurred

since the last read or reset (LF1 and LF2).

3) Detect whether or not a rising edge has occurred

since the last read or reset (LR1 and LR2).

RTP1, LF1, and LR1 represent the data read from

UPIO1; RTP2, LF2, and LR2 represent the data read

from UPIO2.

To issue a read command for the UPIO configured as

GPI, use the command in Table 23.

Once the command is issued, RTP1 and RTP2 provide

the real-time status (0 or 1) of the inputs at UPIO1 or

UPIO2, respectively, at the time of the read. If LF2 or

LF1 is one, then a falling edge has occurred on the

respective UPIO1 or UPIO2 input since the last read or

reset. If LR2 or LR1 is one, then a rising edge has

occurred since the last read or reset.

GPOL outputs a constant low, and GPOH outputs a

constant high. See Figure 6.

TOGG

Use the TOGG input to toggle the DAC outputs

between the values in the input registers and DAC reg-

isters. A delay of greater than 100ns from the end of the

previous write command is required before the TOGG

signal can be correctly switched between the new

value and the previously stored value. When TOGG =

0, the output follows the information in the input regis-

ters. When TOGG = 1, the output follows the informa-

tion in the DAC register (Figure 5).

FAST

The MAX5590–MAX5595 have two settling-time-mode

options: FAST (3µs max) and SLOW (6µs max). To

select the FAST mode, drive FAST low, and to select

SLOW mode, drive FAST high. This overrides (not over-

writes) the SPDA–SPDH bit settings.

Table 23. GPI Read Command

DATA

CONTROL BITS

DATA BITS

DIN1

11101

XXXXX

XXXX

DOUTRB

XXXXX

XXX

RTP2

LF2

LR2

RTP1

LF1

LR1

Table 24. Unipolar Code Table (Gain = +1)

DAC CONTENTS

MSB

LSB

ANALOG OUTPUT

1111

+VREF (4095 / 4096)

1000

0000

0001

+VREF (2049 / 4096)

1000

0000

+VREF (2048 / 4096) = VREF / 2

0111

1111

+VREF (2047 / 4096)

0000

0001

+VREF (1 / 4096)

0000

MAX5590

DAC_

REF_

OUT_

VOUT_ = VREF_ x CODE / 4096

CODE IS THE DAC_ INPUT

CODE (0 TO 4095 DECIMAL).

Figure 7. Unipolar Output Circuit

X = Don’t care.

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