E4257ALPT Semtech, E4257ALPT Datasheet - Page 17

• Manufacturer Part Number: E4257ALPT
• Manufacturer: Semtech

Specifications of E4257ALPT

• Operating Temperature (max): 85C
• Operating Temperature Classification: Commercial
• Mounting: Surface Mount
• Lead Free Status / RoHS Status: Compliant

Common Mode Error/Calibration
In order to attain a high degree of accuracy in a typical
ATE application, offset and gain errors are accounted for
through software calibration. When operating the E42X7
in the Measure Current (MI) or Force Current (FI) modes,
an additional source of error, common mode error, should
be accounted for. Common mode error is a measure of
how the common mode voltage, V
current sense amplifier affects the forced or measured
current values (see Figure 3). Since this error is created
by internal resistors in the current sense amplifier, it is
very linear in nature.
Using the common mode error and common mode linearity
specifications, one can see that with a small number of
calibration steps (see Applications note PMU-A1), the
effect of this error can be significantly reduced.
TEST AND MEASUREMENT PRODUCTS
Circuit Description (continued)
2005 Semtech Corp. / Rev. 5, 11/30/05
Figure 3. Graphical Representation of
(Note: Slope may be negative)
–3.5V
Common Mode Error
2 mV
V OS@IVMON
–2 mV
CM Error = Slope
CM
9.5V
, at the input of the
CM Linearity
V CM@FORCE
Power Supplies
The E42X7 requires four external power supply levels to
operate:
VCC and VEE provide power to all of the E42X7’s internal
analog circuitry except for the internal CMOS transmission
gates used for the analog mux, external PMU switches,
IVMON switches, and the “termination” mode switches.
Power to these switches is provided by the SVCC supply.
This allows for power savings in that the E42X7 can be
used with rail voltages that are less than those that are
being switched using the analog mux or external PMU
switches. Note that in applications where SVCC > VCC,
care must be taken to ensure that SELIPMU = 0 whenever
the FORCE pin voltage exceeds VCC.
Power Supply Sequencing
In order to avoid the possibility of latch-up, the following
power-up requirements must be satisfied:
The following sequence can be used as a guideline when
powering up the E42X7:
The three diode configuration shown in Figure 4 should
be used on a once-per-board basis to prevent damage to
the PMU in the event of a power supply failure and to
ensure that power up requirements are not violated.
17
–
–
–
–
1. VEE
2. VEE
3. GND
1. VEE (substrate)
2. SVCC
3. VCC
4. VDD
5. Digital Inputs
6. Analog Inputs
VCC (Positive Analog Supply)
VEE (Negative Analog Supply)
SVCC (Switch Supply)
VDD (Digital Supply)
E4237/E4257/E4287
GND
All Analog Inputs
All Digital Inputs
VDD
VCC
VCC
VDD
SVCC at all times
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