MAX9951 Просмотр технического описания (PDF) - Maxim Integrated

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MAX9951

Dual Per-Pin Parametric Measurement Units

Maxim Integrated 

Dual Per-Pin Parametric

Measurement Units

“Quick Load” Using Chip Select

If CS goes low and then returns high without any clock

activity, the data from the input registers latch into the

PMU registers. This extra function is not standard for

SPI/QSPI/MICROWIRE interfaces. The quick load mim-

ics the function of LOAD without forcing LOAD low.

Comparators

Two comparators configured as a window comparator

monitor MSR_. THMAX_ and THMIN_ set the high and

low thresholds that determine the window. Both out-

puts are open drain and share a single disable control

that places the outputs in a high-impedance, low-leak-

age state. Table 8 describes the comparator output

states of the MAX9951/MAX9952.

Applications Information

In force-voltage (FV) mode, the voltage at FORCE_ is

directly proportional to the input control voltage. In

force-current (FI) mode, the current flowing out of

FORCE_ is proportional to the input control voltage.

Positive current flows out of the PMU.

In force-nothing (FN) mode, FORCE_ is high impedance.

In measure-current (MI) mode, the voltage at MSR_ is

directly proportional to the current exiting FORCE_.

Positive current flows out of the PMU.

In measure-voltage (MV) mode, the voltage at MSR_ is

directly proportional to the voltage at SENSE_.

Current-Sense-Amplifier

Offset-Voltage Input

IOS is a buffered input to the current-sense amplifiers.

The current-sense amplifiers convert the input control

voltage (IN0_ or IN1_) to the forced DUT current (FI),

Table 8. Comparator Truth Table

(BIT 9)

DISABLE

CONDITION

DUTH DUTL

0

X

High-Z High-Z

1

VMSR > VTHMAX and VTHMIN

0

1

1

VTHMAX > VMSR > VTHMIN

1

1

1

VTHMAX and VTHMIN > VMSR

1

0

1

VTHMIN > VMSR > VTHMAX*

0

0

*VTHMAX > VTHMIN constitutes normal operation. This condition,

however, has VTHMIN > VTHMAX and does not cause any prob-

lems with the operation of the comparators.

and convert the sensed DUT current to the MSR_ out-

put voltage (MI). When IOS equals zero relative to

DUTGND (the GND voltage at the DUT, which the level-

setting DACs and the ADC are presumed to use as a

ground reference), the nominal voltage range that cor-

responds to ±full-scale current is -4V to +4V. Any volt-

age applied to IOS adds directly to this control

input/measure output voltage range, i.e., applying +4V

to IOS forces the voltage range that corresponds to

±full-scale current from 0 to +8V.

The following equations determine the minimum and

maximum currents for each current range correspond-

ing to the input voltage or measure voltage:

VMAXCURRENT = VIOS + 4V

VMINCURRENT = VIOS - 4V

Choose IOS so the limits of MSR_ do not go closer than

2.8V to either VEE or VCC. For example, with supplies of

+10V and -5V, limit the MSR_ output to -2.2V and

+7.2V. Therefore, set IOS between +1.8V and +3.2V.

MSR_ could clip if IOS is not within this range. Use

these general equations for the limits on IOS:

Minimum VIOS = VEE + 6.8V

Maximum VIOS = VCC - 6.8V

Current Booster for Highest Current Range

An external buffer amplifier can be used to provide a

current range greater than the MAX9951/MAX9952

maximum ±64mA output current (Figure 5). This func-

tion operates as follows:

VIN_

MSR_

CCOM_

50Ω

A

EXTSEL_

REXT

RA

RE

FORCE_

DUT

MAIN AMP

E

MAX9951

MAX9952

PMU

XA E

CURRENT- x4

SENSE AMP

SENSE_

Figure 5. External Current Boost

18 ______________________________________________________________________________________

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