ADHV4702-1BCPZ-R7 datasheet(17/22 Pages) AD

17 / 22 page

Data Sheet

ADHV4702-1

THEORY OF OPERATION

analog.com

Rev. D | 17 of 22

Figure 54. SD Pin Response Time, Turning Off

TEMPERATURE MONITOR (TMP)

The ADHV4702-1 features an on-chip temperature sensor in close

proximity to the output stage, where die temperature is the highest.

The output voltage of the temperature sensor appears at the TMP

pin. As an approximate indicator of die temperature, TMP voltage

can be used to monitor power dissipation and implement thermal

shutdown. The TMP voltage at room temperature is nominally 1.9

V, changing at approximately −4.5 mV/°C, as shown in Figure 55.

More precise temperature readings can be achieved through a

one-time room temperature calibration of the TMP pin.

Figure 55. TMP Pin Voltage vs. Junction Temperature

OVERTEMPERATURE PROTECTION

Operation at or beyond the operating temperature specified in the

Absolute Maximum Ratings section can affect product reliability.

To minimize this risk, the ADHV4702-1 features an optional, resis-

tor programmable thermal shutdown where the TMP pin voltage

asserts the SD pin. In addition to proper heat sinking, thermal

shutdown is recommended to protect the amplifier from an overtem-

perature condition. To implement the thermal shutdown function,

tie TMP to SD, as shown in Figure 56, and connect a 200 kΩ

resistor (RTMP) from TMP and SD to DGND in close proximity to the

ADHV4702-1.

Device to device variation in the TMP pin voltage may result in

different shutdown threshold temperatures or shutdown response

times among various devices while implementing the 200 kΩ RTMP.

The shutdown threshold can be adjusted with a smaller RTMP

resistance, yielding a lower threshold temperature.

The RTMP together with the internal resistors of TMP form a voltage

divider that influences the TMP pin reading and TMP voltage drift.

The TMP data in Table 1 and the Temperature Monitor (TMP)

section is only valid when RTMP is uninstalled.

Figure 56. TMP and SD Pin Configuration for Short-Circuit Protection and

Thermal Shutdown

OUTPUT CURRENT DRIVE AND SHORT-

CIRCUIT PROTECTION

The ADHV4702-1 uses an output stage constructed with cascaded,

double diffused, metal-oxide-semiconductor (DMOS) high voltage

transistors that provide wide output swing. The ADHV4702-1 can

typically drive a 20 mA load current continuously. Though with

proper thermal management, the ADHV4702-1 can deliver up to 50

mA. Short-circuit protection is provided by means of the thermal

shutdown feature. To enable short-circuit protection, connect the

SD and TMP pins, and tie both to DGND with a 200 kΩ RTMP.

EXTERNAL COMPENSATION AND CAPACITIVE

LOAD (CLOAD) DRIVING

When driving a CLOAD, the amplifier output resistance and the load

capacitance form a pole in the transfer function of the amplifier. This

additional pole reduces phase margin at higher frequencies and, if

left uncompensated, can result in excessive peaking and instability.

Placing a series resistor (RS) between the amplifier output and

CLOAD (as shown in Figure 57) allows the ADHV4702-1 to drive

capacitive loads beyond 1 μF. Figure 58 shows the series resistor

value vs. load capacitance for a maximum of 2 dB peaking in the

circuit of Figure 57.

In addition to the series resistor, the ADHV4702-1 includes an

optional external compensation feature for driving capacitive loads.

A capacitor (CCOMP) can be installed between COMP and OUT

ADHV4702-1BCPZ-R7 Datenblatt(PDF) 17 Page - Analog Devices

ADHV4702-1BCPZ-R7 Datenblatt(HTML) 17 Page - Analog Devices

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22

Datenblatt Download

Link URL