Thermal Image - Linear Technology DC1948A Demo Manual

positive or negative current monitor configuration
There are both positive and negative current monitors on
the LT3090. The configurations for these two monitors are
different. When the positive current monitor is in use, JP1
needs to be configured on IMP position and JP3 needs to
be configured on +3V position. Meantime a +3V external
power supply needs to be connected to +3V turret. Figure 3
shows this configuration.
Figure 3. Positive Current Monitor Configuration
cable Drop compensation configuration
Demo Circuit 1948A can be configured to evaluate the
cable drop compensation on the LT3090. Note that cable
drop compensation is only using negative current monitor
configuration. JP1, JP3 and R12 shall be configured. JP1
needs to be configured on VIN position. JP3 needs to be

thermal image

An example thermal image shows the temperature distri-
bution on board. The test is complete in still air at room
temperature with 2.1W power dissipation in the LT3090.
This gives the IC case-to-ambient thermal resistance of
about θ
= 24°C/W on the demo board.
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DEMO MANUAL DC1948A
When the negative current monitor is in use, JP1 needs
to be configured on VIN position and JP3 needs to be
configured on IMN position. There is no external power
supply needed. Figure 4 shows this configuration.
Figure 4. Negative Current Monitor Configuration
configured on CDC position. R12 needs be replaced by a
calculated value which has the following relationship with
the total output cable impedance (R
R are both in kΩ:
CBL
R12 = R • 1k
CBL
Figure 5. Temperature Rise at 2.1W Dissipation
) below. R12 and
CBL
dc1948af
3