MAX16947 Maxim, MAX16947 Datasheet - Page 11

• 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

The MAX16946/MAX16947 high-voltage, high-side, cur-
rent-sense LDO/switches feature internal current limiting
to prevent system damage due to fault conditions. The
MAX16946 provides a regulated 8.5V output voltage
fixed or adjustable from 3.3V to 15V. The MAX16946 can
also be configured as a switch, while the MAX16947 is
only available as a switch. The input voltage range for
both devices extends from 4.5V to 18V (45V tolerant),
making the devices ideal for providing phantom power
to remote radio-frequency low-noise amplifiers (LNAs) in
automotive applications.
The devices monitor the load current and provide an
analog output voltage proportional to the sensed load
current. Accurate internal current-limit protects the input
supply against both overload and short-circuit condi-
tions. Two open-drain fault indicator outputs indicate to
the microprocessor when a short circuit, an open-load
condition, or a short-to-battery condition exists. An over-
temperature shutdown is also indicated by means of the
current-sense amplifier’s output voltage.
A fault-blanking feature allows the devices to ignore
momentary faults such as those caused by the charg-
ing of capacitive loads during hot-swapping, prevent-
ing false alarms to the system. The devices feature
short-to-battery protection to latch off the internal LDO/
pass switch during a short-to-battery event and thermal
MAX16946
12
13
14
16
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PIN
MAX16947
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12
13
16
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Detailed Description
Remote Antenna, Current-Sense and
NAME
REG
OUT
OUT
REF
FB
EP
+3V Nominal Reference Output. REF has a current drive capability of 100FA.
Internal Regulator +5V Output. REG powers all internal blocks. Do no use REG to supply
power to external circuitry. Bypass REG to GND with a 1FF capacitor.
Feedback Input (MAX16946 Only). Connect FB to GND to configure the MAX16946 as
a switch. Connect FB to REG for an LDO with a fixed 8.5V output. Connect to the center
tap of an external resistive divider connected between OUT and GND to adjust the
output voltage of the LDO.
Switch or LDO Output (MAX16946 Only). OUT is either a switch or LDO output
depending on the connection of FB.
Switch Output
Exposed Pad (MAX16946 Only). Connect EP to the ground plane for optimal heat
dissipation. Do not use EP as the only electrical ground connection.
overload. They include an active-low, high-voltage-
compatible shutdown input to place them in low-power
shutdown mode.
The integrated current-sense amplifier employs a differ-
ential amplifier that amplifies the voltage between IN and
SENS. A sense resistor, R
and SENS. Typical sense resistor values range between
0.25I and 2I. When the load current passes through
the sense resistor, a voltage drop develops across it.
The current-sense amplifier amplifies this voltage.
The current-sense amplifier features an internally fixed
gain of A
the relationship between the current-sense amplifier
output voltage (V
If LIM is connected to REF, the maximum output voltage
of AOUT is V
3.65V, the maximum output voltage of AOUT extends
to V
always equal to V
AOUT is the output of an internal buffer with 1mA current
drive capability. Bypass AOUT to ground with a 15nF
ceramic capacitor.
AOUT_FS
V
AOUT
(
V
IN
V
FUNCTION
= 26V/V (typ). The following equations show
( )
−
Pin Description (continued)
V
AOUT_FS
V
= 3.65V. The maximum AOUT voltage is
SENS
=
A
AOUT
LIM
V
) ( )
(
V V
, the voltage at LIM.
LDO/Switches
V
= 3V. If LIM is externally driven to
) and load current:
=
)
Current-Sense Amplifier
SENSE
×
I
LOAD
(V
IN
, is connected across IN
−
( )
A
V
SENS
×
R
SENSE
) V
( )
+
( )
Ω
0.4V
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