Silicon Chip – July 2019

siliconchip.com.au Australia’s electronics magazine July 2019 61

T

he ML005-V1.2 is the smallest
module, with a PCB measuring
32 x 32mm. You can purchase it from
AliExpress for around $3.25 (includ-
ing delivery): http://www.aliexpress.com/
item//32853943748.html
The slightly bigger module has no
ID, but its PCB measures 50 x 50mm
and it is available from Banggood
for around $21 (including delivery):
siliconchip.com.au/link/aaof
The largest module, from KKmoon,
comes in an acrylic case, measuring
70 x 52 x 35mm overall. It is available
from suppliers like Banggood and eBay
for around $23 (including delivery):
siliconchip.com.au/link/aaog
Each of the modules are based on
different versions of the AD584 pre-
cision voltage reference device made
by Analog Devices (the datasheet can
be found at siliconchip.com.au/link/

aaoh). Let’s start by looking at how

this chip works.

The AD584 device

Analog Devices describe the AD584

as a “Pin Programmable Precision Volt-

age Reference”. It comes in a number

of versions, all of which are available

in an 8-lead hermetically sealed TO-99

metal package. The two lowest-preci-

sion versions are also available in an

8-lead plastic DIP. The metal package

versions have an “H” suffix, while

those in the plastic package carry the

“NZ” suffix.

All versions are made using laser

wafer trimming (LWT) to adjust the

output voltages and also their tem-

perature coefficients. Originally, five

versions were available: the AD584J,

AD584K and AD584L, all specified

for operation from 0-70°C; and the

AD584S and AD584T, which are speci-

fied for operation between -55°C and

+125°C.

However, the AD584LH version

was discontinued by Analog Devices

in 2012, so presumably, those used in

modules like the one described here

are either ‘new old stock’ (NOS) or

have been ‘recycled’ from used equip-

ment.

The basic specifications of the AD-

584JH, AD584KH and AD584LH are

summarised in Table 1; which can be

found at the end of the article. The

AD584JH version is the least accurate,

while the AD584LH is the most accu-

rate. But note that all three versions

have identical specifications when it

comes to noise output and long-term

stability.

A simplified version of the AD584’s

internal block diagram is shown in

Using Cheap Asian Electronic Modules by Jim Rowe

AD584 Precision

Voltage References

These three low-cost precision voltage

reference modules are based on the AD584

IC from Analog Devices, but each uses

a different version of it and have unique

designs. Two are ‘naked’ boards while the third

comes in a transparent laser-cut acrylic case.