ADHV4702-1BCPZ-R7 datasheet(17/21 Pages) AD

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Data Sheet

ADHV4702-1

Rev. A | Page 17 of 21

100

1000

100

10k

100k

FREQUENCY (Hz)

RADJ = 100kΩ

RADJ = 50kΩ

RADJ = 0Ω

Figure 50. Input Voltage Noise at Various RADJ, TA = 25°C, VS = ±110

SHUTDOWN PIN (SD)

The ADHV4702-1 is equipped with a power saving shutdown

feature. When the SD pin voltage is brought low to within 0.8 V

of DGND, the amplifier is disabled and put in a low power state,

reducing its quiescent current to approximately 0.18 mA.

The SD pin has an internal approximately 400 kΩ pull-up

resistor that enables the amplifier if SD is left floating. When

turning the amplifier on from the shutdown state, pull the SD

pin high to at least 1.6 V above the DGND pin. The SD pin

response time for starting up and coming out of shutdown is

shown in Figure 51 and Figure 52. The SD pin can support

digital logic levels down to 2.5 V. The SD pin can be used to

implement thermal shutdown and short-circuit protection

when used in conjunction with the temperature monitor feature

of the ADHV4702-1.

–1

–0.5

0.5

1.0

1.5

2.0

2.5

3.0

3.5

TIME (50µs/DIV)

SUPPLY CURRENT

SD VOLTAGE

Figure 51. SD Pin Response Time, Turning On

–1

TIME (50µs/DIV)

SUPPLY CURRENT

SD VOLTAGE

–0.5

0.5

1.0

1.5

2.0

2.5

3.0

3.5

Figure 52. 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 53. More precise temperature

readings can be achieved through a one-time room temperature

calibration of the TMP pin.

1.2

1.4

1.6

1.8

2.0

2.2

2.4

–60

–40

–20

100

120

140

JUNCTION TEMPERATURE (°C)

Figure 53. 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, resistor 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 overtemperature condition. To implement the

thermal shutdown function, tie TMP to SD, as shown in Figure 54,

and connect a 200 kΩ resistor (RTMP) from TMP and SD to

DGND in close proximity to the ADHV4702-1.

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