ICL7139CPL Intersil, ICL7139CPL Datasheet - Page 13

• Manufacturer Part Number: ICL7139CPL
• Description: IC DMM 3 3/4 DIGIT AUTORANGE
• Manufacturer: Intersil
• Type: Multimeterr

Specifications of ICL7139CPL

• Rohs Status: RoHS non-compliant
• Voltage Supply Source: Dual ±
• Voltage - Supply: ±24V, 2.7 V ~ 5.25 V
• Operating Temperature: 0°C ~ 70°C
• Mounting Type: Through Hole
• Package / Case: 40-DIP (0.600", 15.24mm)
• Data Interface: -
• Sampling Rate (per Second): -
• Resolution (bits): -

Printed Circuit Board Layout Considerations
Particular attention must be paid to rollover performance,
leakages, and guarding when designing the PCB for a
ICL7139 and ICL7149 based multimeter.
Rollover Performance, Leakages, and Guarding
Because the ICL7139 and ICL7149 system measures very
low currents, it is essential that the PCB have low leakage.
Boards should be properly cleaned after soldering. Areas of
particular importance are: 1) The INT V/
The Triple Point; 3) The R
The conversion scheme used by the ICL7139 and ICL7149
changes the common mode voltage on the integrator and
the capacitors C
cycle. Stray capacitance to ground is charged when this
occurs, removing some of the charge on C
rollover error. Rollover error increases about 1 count for each
picofarad of capacitance between C
and ground, and is seen as a zero offset for positive volt-
ages. Rollover error is not seen as gain error.
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notice. Accordingly, the reader is cautioned to verify that data sheets are current before placing orders. Information furnished by Intersil is believed to be accurate
and reliable. However, no responsibility is assumed by Intersil or its subsidiaries for its use; nor for any infringements of patents or other rights of third parties which
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FIGURE 15. PC BOARD LAYOUT
9
AZ
10
and C
11
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DElNT
lNT
12
during a positive deintegrate
and the C
13
AZ
14 15
or the Triple Point
AZ
and INT l Pins; 2)
lNT
pins.
and causing
ICL7139, ICL7149
3-45
The rollover error causes the width of the +0 count to be
larger than normal. The ICL7139 and ICL7149 will thus read
zero until several hundred microvolts are applied in the posi-
tive direction. The ICL7139 and ICL7149 will read -1 when
approximately -100 V is applied.
The rollover error can be minimized by guarding the Triple
Point and C
(see Figure 15) which is driven by the output of the integra-
tor. Guarding these nodes with the output of the integrator
reduces the stray capacitance to ground, which minimizes
the charge error on C
should be used on both sides of the PC board.
Stray Pickup
While the ICL7139 and ICL7149 have excellent rejection of
line frequency noise and pickup in the DC ranges, any stray
coupling will affect the AC reading. Generally, the analog cir-
cuitry should be as close as possible to the ICL7139 and
ICL7149. The analog circuitry should be removed or
shielded from any 120V AC power inputs, and any AC
sources such as LCD drive waveforms. Keeping the analog
circuit section close to the ICL7139 and ICL7149 will also
help keep the area free of any loops, thus reducing magneti-
cally coupled interference coming from power transformers,
or other sources.
AZ
nodes with a trace connected to the C
lNT
and C
AZ
. If possible, the guarding
lNT
pin,