ISL60002_07 Datasheet, PDF (32/35 Pages) Intersil Corporation – Precision Low Power FGA™ Voltage References

ISL60002
High Current Application
2.502
2.500
V_IN = 5V
2.498
2.496
2.494
V_IN = 3.3V
2.492
2.490
2.488
V_IN = 3.5V
2.486
0
5
10
15
20
25
30
I_LOAD (mA)
FIGURE 114. DIFFERENT V_IN AT ROOM TEMPERATURE
Applications Information
FGA Technology
The ISL60002 series of voltage references use the floating gate
technology to create references with very low drift and supply
current. Essentially the charge stored on a floating gate cell is
set precisely in manufacturing. The reference voltage output
itself is a buffered version of the floating gate voltage. The
resulting reference device has excellent characteristics which
are unique in the industry: very low temperature drift, high initial
accuracy, and almost zero supply current. Also, the reference
voltage itself is not limited by voltage bandgaps or zener
settings, so a wide range of reference voltages can be
programmed (standard voltage settings are provided, but
customer-specific voltages are available).
The process used for these reference devices is a floating
gate CMOS process, and the amplifier circuitry uses CMOS
transistors for amplifier and output transistor circuitry. While
providing excellent accuracy, there are limitations in output
noise level and load regulation due to the MOS device
characteristics. These limitations are addressed with circuit
techniques discussed in other sections.
Nanopower Operation
Reference devices achieve their highest accuracy when
powered up continuously, and after initial stabilization has
taken place. This drift can be eliminated by leaving the
power on continuously.
The ISL60002 is the first high precision voltage reference
with ultra low power consumption that makes it possible to
leave power on continuously in battery operated circuits. The
ISL60002 consumes extremely low supply current due to the
proprietary FGA technology. Supply current at room
temperature is typically 350nA which is 1 to 2 orders of
magnitude lower than competitive devices. Application
circuits using battery power will benefit greatly from having
an accurate, stable reference which essentially presents no
load to the battery.
32
2.502
2.500
5V, +85°C
2.498
2.496
3.2V, +85°C
2.494
2.492
2.490
3.3V, +85°C
2.488
2.486
0
5
10
15
20
I_LOAD (mA)
FIGURE 115. DIFFERENT V_IN AT HIGH TEMPERATURE
In particular, battery powered data converter circuits that
would normally require the entire circuit to be disabled when
not in use can remain powered up between conversions as
shown in Figure 116. Data acquisition circuits providing 12 to
24 bits of accuracy can operate with the reference device
continuously biased with no power penalty, providing the
highest accuracy and lowest possible long term drift.
Other reference devices consuming higher supply currents
will need to be disabled in between conversions to conserve
battery capacity. Absolute accuracy will suffer as the device is
biased and requires time to settle to its final value, or, may not
actually settle to a final value as power on time may be short.
V_IN = +3.0V
10µF
0.01µF
V_{IN VOUT}
ISL60002-25
VOUT = 2.5V
GND
0.001µF–0.01µF
SERIAL
BUS
REF IN
ENABLE
SCK
SDAT
12 to 24-BIT
A/D CONVERTER
FIGURE 116.
Board Mounting Considerations
For applications requiring the highest accuracy, board mounting
location should be reviewed. Placing the device in areas
subject to slight twisting can cause degradation of the accuracy
of the reference voltage due to die stresses. It is normally best
to place the device near the edge of a board, or the shortest
side, as the axis of bending is most limited at that location.
Obviously mounting the device on flexprint or extremely thin PC
material will likewise cause loss of reference accuracy.
FN8082.8
June 4, 2007