E7725AXF datasheet(13/39 Pages) SEMTECH

13 / 39 page

TEST AND MEASUREMENT PRODUCTS

Edge7725

www.semtech.com

Circuit Description (continued)

Load Commutating Voltage Compensation

The VCM_CAP pin is an op amp compensation node that

requires a fixed 10 nanofarad chip capacitor (with good

high frequency characteristics) to ground. This capacitor

is used to compensate an internal node on the on-chip

buffer for the commutating voltage input.

The VCM_OUT is the actual commutating voltage gener-

ated by the on-chip buffer. VCM_OUT is also connected to

the diode bridge. A capacitor of 0.1 µF to ground is also

needed on the VCM_OUT pin for high speed switching of

the load currents.

Load Power Down Mode

Referring to Table 1, the load circuit can be placed in the

power down state in certain configurations which reduces

overall power consumption. In other configurations, the

load remains powered and ready for operation.

Thermal Monitor

An on-chip thermal diode string of five diodes in series ex-

ists (see figure below). This string allows accurate die tem-

perature measurements.

An external bias current of 100 µA is injected through the

string, and the measured voltage corresponds to a spe-

cific junction temperature with the following equation:

Tj[°C]={(ANODE – CATHODE) / 5 – 0.768} / (–0.00169).

Power Supply Sequencing

In order to avoid the possibility of latch-up, the following

power-up requirements must be satisfied:

1. VEE < GND < VCC at all times

2. VEE < Analog Inputs < VCC

3. VEE < Digital Iputs < input max voltage or

VCC, whichever is less

The following sequencing can be used as a guideline when

powering up the Edge7725:

1. VEE

2. VCC

3. Digital Inputs

4. Analog Inputs

The recommended power-down sequence is the reverse

order of the power-up sequence.

ANODE

CATHODE

Temperature Coefficient =

-7.9 mV / °C

Bias Current

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