AD8460 datasheet(29/75 Pages) AD

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Data Sheet

AD8460

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Rev.0

29 of 75

The maximum output swing is established by the internal DAC configuration. See FULL-SCALE

ADJUSTMENT.

The AD8460 requires dual high voltage (up to ±55 V) power supplies at HVCC and HVEE, and a single low

voltage (5 V) power supply at VCC_5V. The part generates 3.3 V internally from a LDO output at AVDD_3P3V,

and DVDD_3P3V is an internal digital supply bypass point that should be connected to AVDD_3P3V. See

POWER SUPPLIES AND DECOUPLING.

A reference of 5 V is required at VREF_5V to provide the reference voltage for analog low voltage and

protection threshold DACs. Connect VREF_5V to an external 5 V reference or to VCC_5V (reduced accuracy).

The AD8460 utilizes a reference of 1.2 V at REFIO_1P2V to provide the reference voltage for the high-speed

DAC. Connect REFIO_1P2V to an external 1.2 V reference or float to use the internal 1.2 V reference, which

can give rise to reduced accuracy. See REFERENCE OPERATION. An external resistor RSET connected to

FS_ADJ establishes the internal DAC’s reference current IREF. When RSET = 2 kΩ, as in Figure 58,the DAC’s

full scale complementary output currents are set to the nominal value of 20 mA. See FULL-SCALE

ADJUSTMENT.

The DAC and the high-voltage, high-current (HV-HI) output driver can be connected externally through

pin IOUTP and INP on the high side, and pin IOUTN and INN on the low side. The termination resistors

(RTERM) set the inputs to the HV-HI driver. The RTERM resistors are recommended to be high precision 50 Ω.

The % tolerance on the RTERM corresponds to possible error at the output. Typically, a tolerance of 0.1% is

recommended in systems that balance precision and cost. 0.01% resistors are recommended for higher

precision systems.

In addition to drive capability, the AD8460 provides a suite of features relating to fault monitoring and load

protection. The part features a junction temperature monitor providing voltage at output indicating junction

temperature up to 2.5 V at maximum junction temperature of 150 °C. The digital engine allows for programmable

output current limit (source current and/or sink current), programmable output voltage limit (positive voltage

and/or negative voltage), and programmable temperature limit (maximum junction temperature). See SHUTDOWN

PROTECTION SETTINGS.

INITIAL POWER-UP

POWER SUPPLIES AND DECOUPLING

The AD8460 requires dual high voltage supplies in the range of ±12 V to ±50 V at HVCC and HVEE, as well as a single

5 V low voltage supply at VCC_5V. Bypass all supply pins to ground using high quality, low ESR 0.1 μF capacitors.

Place bypass capacitors as close to the supply pins as possible, with a short, direct connection to the PCB’s analog

ground plane. Additionally, place four 1.2 μF ceramic capacitors from each high voltage supply to ground to

provide good low frequency bypassing, and to provide the needed current to support large, fast-slewing signals.

Low-inductance planes are recommended for high voltage supply routing.

AVDD_3P3V is the analog supply bypass point for the internal 3.3 V LDO. AVDD_3P3V requires a 0.1 µF bypass

capacitor from AVDD_3P3V to GND. Connect AVDD_3P3V to DVDD_3P3V.

VREF_5V

VREF_5V sets the reference voltage for internal alarm threshold DACs and needs to be biased. A precise 5 V

reference IC is recommended. Alternatively, VREF_5V can be connected to VCC_5V (reduced accuracy).

AD8460 Datasheet(PDF) 29 Page - Analog Devices

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