ISL71090SEH75 Datasheet, PDF (9/13 Pages) Intersil Corporation – RH voltage regulators precision outputs

ISL71090SEH75
Device Operation
Bandgap Precision Reference
The ISL71090SEH75 uses a bandgap architecture and special
trimming circuitry to produce a temperature compensated,
precision voltage reference with high input voltage capability and
moderate output current drive.
Applications Information
Board Mounting Considerations
For applications requiring the highest accuracy, board mounting
location should be reviewed. The device uses a ceramic flatpack
package. Generally, mild stresses to the die when the Printed
Circuit (PC) board is heated and cooled, can slightly change the
shape. Because of these die stresses, placing the device in areas
subject to slight twisting can cause degradation of reference
voltage accuracy. It is normally best to place the device near the
edge of a board, or on the shortest side, because the axis of
bending is most limited in that location. Mounting the device in a
cutout also minimizes flex. Obviously, mounting the device on
flexprint or extremely thin PC material will likewise cause loss of
reference accuracy.
Board Assembly Considerations
Some PC board assembly precautions are necessary. Normal
output voltage shifts of typically 100µV can be expected with
Pb-free reflow profiles or wave solder on multilayer FR4 PC
boards. Precautions should be taken to avoid excessive heat or
extended exposure to high reflow or wave solder temperatures.
Noise Performance and Reduction
The output noise voltage over the 0.1Hz to 10Hz bandwidth is
typically 1.0µV_P-P (V_OUT = 7.5V). The noise measurement is made
with a 9.9Hz bandpass filter. Noise in the 10Hz to 1kHz
bandwidth is approximately 1.2µV_RMS, with 1µF capacitance on
the output. This noise measurement is made with a bandpass
filter of 990Hz. Load capacitance up to 10µF (with COMP
capacitor listed in Table 2) can be added but will result in only
marginal improvements in output noise and transient response.
Turn-On Time
Normal turn-on time is typically 250µs, the circuit designer must
take this into account when looking at power-up delays or
sequencing.
Temperature Coefficient
The limits stated for temperature coefficient (Tempco) are
governed by the method of measurement. The overwhelming
standard for specifying the temperature drift of a reference is to
measure the reference voltage at two temperatures, which
provide for the maximum voltage deviation and take the total
variation, (V_HIGH - V_LOW), this is then divided by the temperature
extremes of measurement (T_HIGH – T_LOW). The result is divided by
the nominal reference voltage (at T = +25°C) and multiplied by
10⁶ to yield ppm/°C. This is the “Box” method for specifying
temperature coefficient.
Output Voltage Adjustment
The output voltage can be adjusted above and below the
factory-calibrated value via the trim terminal. The trim terminal is
the negative feedback divider point of the output op amp. The
voltage at the trim pin is set at approximately 1.216V by the internal
bandgap and amplifier circuitry of the voltage reference. The
suggested method to adjust the output is to connect a 1MΩ external
resistor directly to the trim terminal and connect the other end to the
wiper of a potentiometer that has a 100kΩ resistance and whose
outer terminals connect to VOUT and ground. If a 1MΩ resistor is
connected to trim, the output adjust range will be ±6.3mV. The TRIM
pin should not have any capacitor tied to its output, also it is
important to minimize the capacitance on the trim terminal during
layout to preserve output amplifier stability. It is also best to connect
the series resistor directly to the trim terminal to minimize that
capacitance and also to minimize noise injection. Small trim
adjustments will not disturb the factory-set temperature coefficient
of the reference, but trimming near the extreme values can.
Output Stage
The output stage of the device has a push-pull configuration with
an high-side PNP and a low-side NPN. This helps the device to act
as a source and sink. The device can source 20mA.
Use of COMP Capacitor
The reference can be compensated for the C_OUT capacitors used
by adding a capacitor from COMP pin to GND. See Table 2 for
recommended values. of the COMP capacitor.
C_OUT
(µF)
0.1
1
10
TABLE 2.
C_COMP
(nF)
1
1
10
SEE Testing
The SET result is based on the ISL71090SEH25. The
ISL71090SEH25 and ISL71090SEH75 share the same active
circuitry consisting of a precision bandgap circuit and a trimmable
amplifier to set the output reference with only a resistor change to
scale the output. The SET test was done under an ion beam having
an LET of 86MeV•cm²/mg. The device did not latch up or burn out
to a V_DD of 36V and at +125°C. Single Event transients were
observed and are summarized in the Table 3:
TABLE 3.
V_IN
I_OUT
C_OUT
SET
(V)
(mA)
(µF)
(% V_OUT)
4
5
1
-4.6
30
5
1
-4.4
30
5
10
-1.0
DNC Pins
These pins are for trimming purposes and for factory use only. Do
not connect these to the circuit in any way. It will adversely effect
the performance of the reference.
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9
FN8591.3
March 18, 2016