AD780AN Analog Devices Inc, AD780AN Datasheet - Page 5

• Manufacturer Part Number: AD780AN
• Description: IC PREC V-REF 2.5V/3.0V 8-DIP
• Manufacturer: Analog Devices Inc

Specifications of AD780AN

• Mounting Type: Through Hole
• Rohs Status: RoHS non-compliant
• Design Resources: Using AD8599 as an Ultralow Distortion Driver for the AD7991 (CN0043) Using AD8599 as an Ultralow Distortion Driver for the AD7995 (CN0044) Using AD8599 as an Ultralow Distortion Driver for the AD7999 (CN0045) Using AD7328 in Appls with Single-Ended Industrial-Level Signals (CN0047) AD5382 Channel Monitor Function (CN0012) AD5383 Channel Monitor Function (CN0015) AD5390/91/92 Channel Monitor Function (CN0030) Measuring -48 V High-Side Current Using AD629, AD8603, AD780, and AD7453 (CN0100) High Voltage, High Precision Current Sensing with Output Level Shifting Using AD8210 and AD8274 (CN0116)
• Reference Type: Series and Shunt, Programmable
• Voltage - Output: 2.5V, 3V
• Tolerance: ±5mV
• Temperature Coefficient: 7ppm/°C
• Voltage - Input: 4 ~ 36 V
• Number Of Channels: 1
• Current - Quiescent: 1mA
• Current - Output: 10mA
• Operating Temperature: -40°C ~ 85°C
• Package / Case: 8-DIP (0.300", 7.62mm)
• Operating Temperature Max: 85°C
• Peak Reflow Compatible (260 C): No
• Output Voltage: 2.5V
• Current Rating: 1mA
• Output Voltage Max: 2.5V
• Leaded Process Compatible: No
• Features: 1mA
• Current - Cathode: -
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant

THEORY OF OPERATION
Band gap references are the high performance solution for low
supply voltage and low power voltage reference applications. In
this technique, a voltage with a positive temperature coefficient
is combined with the negative coefficient of a transistor’s V
produce a constant band gap voltage.
In the AD780, the band gap cell contains two NPN transistors
(Q6 and Q7) that differ in emitter area by 12×. The difference in
their V
produces a PTAT voltage across R4 that, when combined with
the V
temperature. Precision laser trimming of the resistors and other
patented circuit techniques are used to further enhance the drift
performance.
be
be
TEMP
of Q7, produces a voltage (V
s produces a PTAT current in R5. This, in turn,
NC = NO CONNECT
NC
1
3
AD780
R10
Q6
Figure 4. Schematic Diagram
+V
2
R5
R4
IN
R11
GND
Q7
4
bg
R14
) that does not vary with
NC
O/P SELECT
2.5V – NC
3.0V – GND
7
8
R13
R15
R16
6
5
V
TRIM
OUT
be
to
Rev. E | Page 5 of 12
The output voltage of the AD780 is determined by the
configuration of Resistors R13, R14, and R15 in the amplifier’s
feedback loop. This sets the output to either 2.5 V or 3.0 V,
depending on whether R15 (Pin 8) is grounded or not
connected.
A unique feature of the AD780 is the low headroom design of
the high gain amplifier, which produces a precision 3 V output
from an input voltage as low as 4.5 V (or 2.5 V from a 4.0 V
input). The amplifier design also allows the part to work with
+V
This allows the AD780 to work as a 2-terminal shunt regulator,
providing a −2.5 V or −3.0 V reference voltage output without
external components.
The PTAT voltage is also used to provide the user with a
thermometer output voltage (at Pin 3) that increases at a rate of
approximately 2 mV/°C.
The AD780’s NC (Pin 7) is a 20 kΩ resistor to +V
solely for production test purposes. Users who are currently
using the LT1019 self-heater pin (Pin 7) must take into account
the different load on the heater supply.
IN
= V
OUT
when current is forced into the output terminal.
IN
that is used
AD780