MAX16913AGEE(2015) Просмотр технического описания (PDF) - Maxim Integrated
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MAX16913AGEE Datasheet PDF : 12 Pages
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MAX16913/MAX16913A
Remote Antenna Current-Sense
Amplifier and Switches
Detailed Description
The MAX16913/MAX16913A high-voltage, high-side,
current-sense switches feature internal current limiting
to prevent system damage due to fault conditions. The
MAX16913/MAX16913A input voltage range extends
from 5V to 18V, making them ideal for providing phantom
power to remote radio-frequency low-noise amplifiers
(LNAs) in automotive applications. High-side current mon-
itoring does not interfere with the ground path of the load
being measured, making these devices particularly useful
in a wide range of high-voltage battery-powered systems.
The MAX16913/MAX16913A monitor the load current by
means of a high-side current-sense amplifier and provide an
analog output voltage proportional to that current at AOUT.
The devices combine a high-side current-sense
amplifier, an internal switch, a +3V bandgap reference,
and two open-drain fault indicator outputs. These fea-
tures enable the design of remote power circuits with
short-circuit, short-to-battery, and thermal protection. For
the MAX16913A, the open-load threshold is externally
adjustable using a resistive divider.
A fault-blanking feature enables the circuit to ignore
momentary faults, such as those caused by initial
charging of a capacitive load at turn-on, preventing false
alarms to the system.
The MAX16913/MAX16913A provide an active-high
control input (SHDN) to put the devices in low-power
shutdown mode.
Current-Sense Amplifier
The integrated current-sense amplifier is a differential
amplifier that amplifies the voltage between VIN and
VSENS. A sense resistor (0.65Ωmin, 4.7Ωmax), RSENSE,
is connected across VIN and VSENS. 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 13V/V (typ). The following equations show the
relationship between the current-sense amplifier output
voltage (AOUT) and load current:
I
LOAD(
A
)
=
(VIN-VSENS )(V)
R SENSE(Ω)
VA= OUT(V) A V (V/V) × (VIN-VSENS )(V)+ 0.4V
AOUT is the output of an internal buffer with a 5kΩ output
impedance.
The AOUT voltage is clamped to typically 4.3V in order to
avoid damage to external circuitry.
Load Protection
The MAX16913/MAX16913A monitor the load current
through an external sense resistor and perform the
following actions:
● If the monitored current is lower than the open-load
current, the device signals open load (see the Current-
Sense Amplifier” section).
● If the monitored current is higher than the short-circuit
current (ISC), the device enters the short-circuit mode
(see the Short Circuit section).
The devices also perform a short-to-battery detection
every time the internal switch turns on (see the Short-to-
Battery Detection section). In addition, thermal shutdown
protects the MAX16913/MAX16913A from overheating
(see the Thermal Shutdown section). Two open-drain out-
puts (OL and SC) indicate the device status (see Table 1).
Open Load
If the load current drops below the open-load current
threshold, the OL output asserts low. An open-load
condition does not turn off the internal switch. The
MAX16913 provides an internally fixed open-load
threshold, while the MAX16913A features an adjustable
open-load threshold.
For the MAX16913, when (VIN - VSENS) drops below
20mV (typ), the device signals open load.
For the MAX16913A, using a resistive divider between
REF, the open-load threshold adjustment pin (OLT), and
GND sets the open-load threshold (see the Open-Load
Threshold Selection section).
Table 1. Status Truth Table
SC OL
0 0 0.4V
VAOUT
0 1 Cycling While Autoretrying
1 0 0.4V
1 1 (VIN - VSENS) x 13 + 0.4V
DEVICE STATUS
OUT Short-to-Battery
Short-Circuit Condition
Open-Load Condition
Normal Operation
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