AD5560JSVUZ datasheet(59/68 Pages) AD

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Data Sheet

AD5560

Rev. D | Page 59 of 68

USING THE HCAVDDx AND HCAVSSx SUPPLIES

The first set of power supplies, AVDD and AVSS, 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, HCAVSS1 and HCAVDD1,

are intended to be used to minimize power consumption in

the AD5560 device for the EXTFORCE1 range (up to ±1.2 A).

Similarly, the HCAVSS2 and HCAVDD2 supplies are used for the

EXTFORCE2 range (up to ±500 mA). These supplies must be

less than or equal to the AVDD and AVSS supplies. When driving

high currents at low voltages, power can be greatly minimized

by ensuring that the supplies are at the lowest voltages.

Therefore, HCAVSSx and HCAVDDx 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 HCAVDDx

and HCAVSSx 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 AVDD and AVSS supplies can support the high

voltage needs, whereas the HCAVDDx and HCAVSSx supplies

support the low voltage, higher current ranges. Diode selection

should take into account the current carrying requirements.

Supply selection for HCAVDDx and HCAVSSx 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 AVDD and AVSS supplies

must be applied to the device either before or at the same time

as the HCAVDDx and HCAVSSx supplies, as indicated in Table 3.

There are no known supply sequences surrounding the DVCC

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 RSENSE

±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 RSENSE

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 RSENSE

10µF

0.1µF

10µF

0.1µF

HCAVDD2 = +9V

HCAVSS2 = –5V

HCAVDD1 = +6V

HCAVSS1 = –5V

10µF

0.1µF

10µF

0.1µF

AVDD = +28V

AVSS = –5V

10µF

0.1µF

DVCC = 3V/5V

0.1µF

10µF

0.1µF

33kΩ

100kΩ

Figure 59. Example of Using the Extra Supply Rails Within the AD5560 to Achieve Multiple Voltage/Current Ranges

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