MAX16947 Maxim, MAX16947 Datasheet - Page 16

• Manufacturer Part Number: MAX16947
• Description: The MAX16946/MAX16947 high-voltage, high-side, current-sense LDO/switches feature internal current limiting to prevent system damage due to fault conditions
• Manufacturer: Maxim

Remote Antenna, Current-Sense and
LDO/Switches
Ideally, the maximum load current develops the full-scale
sense voltage across the current-sense resistor. The
current-sense amplifier output voltage is given by:
where V
amplifier, and A
fier of 26V/V (typ).
Calculate the maximum value for R
amplified differential voltage across IN and SENS does
not exceed the short-circuit AOUT voltage threshold
of V
Characteristics table:
Typical sense resistor values range between 0.25I and
2I.
During normal operation, when the load current is less
than the short-circuit current threshold, the maximum
AOUT voltage is equal to V
ground is present and the device goes into autoretry,
the maximum AOUT voltage extends to V
age at LIM.
Keep inductance low if I
frequency component. Wire-wound resistors have the
highest inductance, while metal film is somewhat better.
Low-inductance, metal-film resistors are also available.
Instead of being spiral wrapped around a core, as in
Figure 5. Open-Load Current Threshold Selection
16
SC
_____________________________________________________________________________________
= 1.7V (typ), which is defined in the Electrical
AOUT
R
V
SENSE
AOUT
is the output voltage of the current-sense
V
Applications Information
= A
is the gain of the current-sense ampli-
=
Choosing the Sense Resistor
I
MAX16946
MAX16947
LOAD(FULL_SCALE)
V
x (V
IN
V
SENSE
SC
SC
- V
REF
OLT
. When a short circuit to
−
SENS
0.4V
has a large high-
SENSE
) + 0.4V
R
R
1
2
×
A
LIM
, so that the
V
, the volt-
metal-film or wire-wound resistors, they are a straight
band of metal and are available in values under 1I.
Because of the high current that flows through R
eliminate parasitic trace resistance from causing errors
in the sense voltage.
A resistive divider between REF, OLT, and GND sets the
open-load current threshold. See Figure 5.
Use the following formula to set the desired open-load
current threshold:
where I
A
and V
R
resistive dividers used to set the open-load and current-
limit thresholds does not exceed the REF output 100FA
drive capability.
For example, to set the open-load current threshold at
10mA, using a 0.5I sense resistor, use the following
method to calculate the value of R
Choose R
Figure 6. Current-Limit Threshold Selection
V
2
large enough so that the equivalent resistance of the
is the current-sense amplifier gain (26V/V typical),
Open-Load Current Threshold Selection
REF
OL
R
1
R
is the reference voltage (3V typ). Size R
2
is the desired open-load current threshold,
2
= 470kI and calculate R
=
=






0.5
R
SENSE
Ω ×
MAX16946
MAX16947
0.01A 26V/V+0.4V
×
I
V
OL
REF
3V
×
R
R
REF
LIM
×
1
1
A
V
1
+
and R
2
0.4V
R
R
as 100kI.
1
2
2
−
:
−
1
1






SENSE
1
and
,