Datasheet

Data Sheet AD5560
Rev. D | Page 59 of 68
USING THE HCAV
DD
x AND HCAV
SS
x SUPPLIES
The first set of power supplies, AV
DD
and AV
SS
, provide power
to the DAC levels and associated circuitry. They also supply the
force amplifier stage for the low current ranges (ranges using
internal sense resistors up to 25 mA maximum).
The second set of power supplies, HCAV
SS
1 and HCAV
DD
1,
are intended to be used to minimize power consumption in
the AD5560 device for the EXTFORCE1 range (up to ±1.2 A).
Similarly, the HCAV
SS
2 and HCAV
DD
2 supplies are used for the
EXTFORCE2 range (up to ±500 mA). These supplies must be
less than or equal to the AV
DD
and AV
SS
supplies. When driving
high currents at low voltages, power can be greatly minimized
by ensuring that the supplies are at the lowest voltages.
Therefore, HCAV
SS
x and HCAV
DD
x can be switched externally
to different power rails as required by the set voltage range.
However, the design of the high current output stage means
that these supplies always have to be at a higher voltage than
the forced voltage, irrespective of the current range being used.
Therefore, depending on the level of supply switching, external
diodes may be required in series with each of the HCAV
DD
x
and HCAV
SS
x supplies, as shown in Figure 59. There are
internal pull-up resistors between the supplies (see Figure 59).
Using diodes here allows a more flexible use of supplies and
can minimize the amount of supply switching required. In the
example, the AV
DD
and AV
SS
supplies can support the high
voltage needs, whereas the HCAV
DD
x and HCAV
SS
x supplies
support the low voltage, higher current ranges. Diode selection
should take into account the current carrying requirements.
Supply selection for HCAV
DD
x and HCAV
SS
x supplies must
allow for this extra voltage drop.
POWER SUPPLY SEQUENCING
When the supplies are connected to the AD5560, it is important
that the AGND and DGND pins be connected to the relevant
ground plane before the positive or negative supplies are applied.
In most applications, this is not an issue because the ground
pins for the power supplies are connected to the ground pins of
the AD5560 via ground planes. The AV
DD
and AV
SS
supplies
must be applied to the device either before or at the same time
as the HCAV
DD
x and HCAV
SS
x supplies, as indicated in Table 3.
There are no known supply sequences surrounding the DV
CC
supply, although it is recommended that it be applied as
indicated by the absolute maximum ratings (see Table 3).
AD5560
33kΩ
1200mA
RANGE
500mA
RANGE
FORCE
DUT RANGE
0V TO +25V
OUTPUT RANGE
0V TO +25V
INTERNAL R
SENSE
±0.5V AT FULL CURRENT
INTERNAL RANGE SELECT
(5µA, 25µA, 250µA, 2.5mA, 25mA)
EXTFORCE1
DUT RANGE
–2V TO +3V
EXTFORCE2
DUT RANGE
0V TO +6V
ALLOW ±0.5V
FOR EXT R
SENSE
OUTPUT RANGE
–2.5V TO +3.5V
2. HIGHEST CURRENT
RANGE
1. LOW CURRENT,
HIGH VOLTAGE
3. MIDCURRENT
RANGE
OUTPUT RANGE
–0.2V TO +6.5V
ALLOW ±0.5V FOR EXT R
SENSE
+
10µF
+
0.1µF
10µF
0.1µF
HCAV
DD
2 = +9V
HCAV
SS
2 = –5V
HCAV
DD
1 = +6V
HCAV
SS
1 = –5V
+
+
+
10µF
+
0.1µF
10µF
0.1µF
+
+
AV
DD
= +28V
AV
SS
= –5V
+
10µF
+
0.1µF
DV
CC
= 3V/5V
+
0.1µF
10µF
0.1µF
++
33kΩ
100kΩ
100kΩ
07779-012
Figure 59. Example of Using the Extra Supply Rails Within the AD5560 to Achieve Multiple Voltage/Current Ranges