MAX5184BEEG+ Datasheet MAX5184ETG+, MAX5181BEEG+, MAX5184BEEG+ | P7-P9

MAX5181/MAX5184

10-Bit, 40MHz, Current/Voltage-Output DACs

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Pin Description

QSOP TQFN

NAME FUNCTION

1 22 CREF REFO

2 23 OUTP Positive Analog Output. Current output for MAX5181; voltage output for MAX5184.

3 24 OUTN Negative Analog Output. Current output for MAX5181; voltage output for MAX5184.

4 1 AGND Analog Ground

52AV

Analog Positive Supply, 2.7V to 3.3V

6 3 DACEN

DAC Enable, Digital Input

0: Enter DAC standby mode with PD = DGND

1: Power-up DAC with PD = DGND

X: Enter shutdown mode with PD = DVDD (X = don’t care)

74PD

Power-Down Select

0: Enter DAC standby mode (DACEN = DGND) or power-up DAC (DACEN = DVDD)

1: Enter shutdown mode

85CS Active-Low Chip Select

9 6 CLK Clock Input

10 7 REN Active-Low Reference Enable. Connect to DGND to activate on-chip 1.2V reference.

11 8 D0 Data Bit D0 (LSB)

12–19 9–16 D1–D8 Data Bits D1–D8

20 17 D9 Data Bit D9 (MSB)

21 18 DV

Digital Supply, 2.7V to 3.3V

22 19 DGND Digital Ground

23 20 REFR Reference Input

24 21 REFO Reference Output

— — EP

Exposed Pad (TQFN Only). Internally connected to AGND. Connected to the analog

ground plane (AGND).

MAX5181/MAX5184

10-Bit, 40MHz, Current/Voltage-Output DACs

8 _______________________________________________________________________________________

Detailed Description

The MAX5181/MAX5184 are 10-bit digital-to-analog con-

verters (DACs) capable of operating with clock speeds

up to 40MHz. Each converter consists of separate input

and DAC registers, followed by a current source array

capable of generating up to 1.5mA full-scale output cur-

rent (Figure 1). An integrated 1.2V voltage reference and

control amplifier determine the data converters’ full-scale

output currents/voltages. Careful reference design

ensures close gain matching and excellent drift charac-

teristics. The MAX5184’s voltage output operation fea-

tures matched 400Ω on-chip resistors that convert the

current-array current into a voltage.

Internal Reference and

Control Amplifier

The MAX5181/MAX5184 provide an integrated 50ppm/°C,

1.2V, low-noise bandgap reference that can be dis-

abled and overridden by an external reference voltage.

REFO serves either as an external reference input or an

integrated reference output. If REN is connected to

DGND, the internal reference is selected and REFO

provides a 1.2V output. Due to its limited 10µA output

drive capability, REFO must be buffered with an exter-

nal amplifier, if heavier loading is required.

The MAX5181/MAX5184 also employ a control amplifier

designed to regulate simultaneously the full-scale out-

put current (I

) for both outputs of the devices. The

output current is calculated as follows:

= 8  I

REF

where I

REF

is the reference output current (I

REF

REFO

SET

) and I

is the full-scale output current.

SET

is the reference resistor that determines the

amplifier’s output current on the MAX5181 (Figure 2).

This current is mirrored into the current source array,

where it is equally distributed between matched current

segments and summed to valid output current readings

for the DACs.

The MAX5184 converts this output current into a differ-

ential output voltage (V

OUT

) with two internal, ground-

referenced 400Ω load resistors. Using the internal 1.2V

reference voltage, the MAX5184’s integrated

9.6kΩ*

REFR

REFO

1.2V REF

REN

CURRENT-

SOURCE ARRAY

DAC SWITCHES

400Ω*

OUTP

OUTN

400Ω*

MSB

DECODE

CLK

OUTPUT

LATCHES

OUTPUT

LATCHES

INPUT

LATCHES

*INTERNAL 400Ω AND 9.6kΩ

RESISTORS FOR MAX5184 ONLY.

INPUT

LATCHES

AGND CS DACEN PD

DGND

CREF

MAX5181

MAX5184

MSB

DECODE

D9–D0

Figure 1. Functional Diagram

MAX5181/MAX5184

10-Bit, 40MHz, Current/Voltage-Output DACs

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reference output-current resistor (R

SET

= 9.6kΩ) sets

REF

to 125µA and I

to 1mA.

External Reference

To disable the MAX5181/MAX5184’s internal reference,

connect REN to DV

. A temperature-stable, external

reference may now be applied to drive the REFO pin to

set the full-scale output (Figure 3). Choose a reference

capable of supplying at least 150µA to drive the bias

circuit that generates the cascode current for the cur-

rent array. For improved accuracy and drift perfor-

mance, choose a fixed output voltage reference such

as the 1.2V, 25ppm/°C MAX6520 bandgap reference.

Standby Mode

To enter the lower-power standby mode, connect digital

inputs PD and DACEN to DGND. In standby, both the

reference and the control amplifier are active with the

current array inactive. To exit this condition, DACEN

must be pulled high with PD held at DGND. The

MAX5181/MAX5184 typically require 50µs to wake up

and let both outputs and the reference settle.

Shutdown Mode

For lowest power consumption, the MAX5181/MAX5184

provide a power-down mode in which the reference, con-

trol amplifier, and current array are inactive and the DAC

supply current is reduced to 1µA. To enter this mode,

connect PD to DV

. To return to active mode, connect

PD to DGND and DACEN to DV

. About 50µs are

required for the parts to leave shutdown mode and settle

to their outputs’ values prior to shutdown. Table 1 lists the

power-down mode selection.

Timing Information

Figure 4 shows a detailed timing diagram for the

MAX5181/MAX5184. With each high transition of the

clock, the input latch is loaded with the digital value set

by bits D9 through D0. The content of the input latch is

then shifted to the DAC register, and the output up-

dates at the rising edge of the next clock.

Outputs

The MAX5181 output is designed to supply full-scale

output currents of 1mA into 400Ω loads in parallel with

a capacitive load of 5pF. The MAX5184 features inte-

grated 400Ω resistors that restore the array current to

proportional, differential voltages of 400mV. These dif-

ferential output voltages can then be used to drive a

balun transformer or a low-distortion, high-speed oper-

ational amplifier to convert the differential voltage into a

single-ended voltage.

SET

9.6kΩ

SET

COMP

REFR

AGND

DGND

REF

REFO

MAX4040

SET

1.2V

BANDGAP

REFERENCE

REN

CURRENT-

SOURCE ARRAY

*COMPENSATION CAPACITOR (C

COMP

= 100nF) **9.6kΩ REFERENCE CURRENT-SET RESISTOR

INTERNAL TO MAX5184 ONLY. USE EXTERNAL

SET

FOR MAX5181.

OPTIONAL EXTERNAL BUFFER

FOR HEAVIER LOADS

MAX5181

MAX5184

Figure 2. Setting I

with the Internal 1.2V Reference and the Control Amplifier

P1-P3 P4-P6 P7-P9 P10-P12 P13-P15 P16-P16

MAX5184BEEG+

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Digital to Analog Converters - DAC 10-Bit High Speed DAC

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