MAX16947 Maxim, MAX16947 Datasheet - Page 12

• 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
The devices monitor the load current through an external
sense resistor and perform the following actions:
U If the monitored current is lower than the set open-
U If the monitored current is greater than the set short-
The devices also perform a short-to-battery detection
before the internal switch turns on. During normal opera-
tion, reverse-current detection protects the devices from
short-to-battery events (see the Short-to-Battery and
Reverse-Current Detection section).
In addition, thermal shutdown protects the devices from
overheating (see the Thermal Shutdown section).
Two open-drain fault indicator outputs (OL and SC) and the
AOUT voltage indicate the devices’ status (Table 1).
If the load current drops below the open-load cur-
rent threshold, the OL output latches low. An open-
load condition does not turn off the internal switch. To
unlatch the OL output, pulse SHDN low for less than
t
t
The open-load current threshold is adjustable. Connect
a resistive divider between REF, the open-load current
threshold adjustment input (OLT), and GND to set the
open-load current threshold (see the Open-Load Current
Threshold Selection section).
12
SHDN_OFF
SHDN_OFF
load current, the devices signal that there is an open-
load (see the Open Load section).
circuit current (I
circuit mode (see the Short Circuit and Current Limit
section).
_____________________________________________________________________________________
(150Fs min). Keeping SHDN low for longer than
shuts down the device.
SC
), the devices enter the short-
Load Protection
Open Load
If the load current exceeds the set short-circuit cur-
rent threshold (I
During this period, the load current is limited to the
current limit set by the voltage at LIM. If the overcurrent
condition persists beyond t
the internal switch turns off. The timer resets if the over-
current condition disappears before the blanking time
(t
If the switch is turned off at the end of t
timer (t
has elapsed, and during that time the switch stays off.
At the end of t
SC stays low. If the fault still exists, the cycle repeats. If
the fault has been removed, the switch stays on and SC
goes high after the blanking time t
when the switch is off, the current through the switch is
zero. Blanking time and retry time have fixed values of
100ms (min) and 1100ms (min), respectively.
Figures 1–4 show the response of the devices to the
presence and removal of overcurrent conditions.
The current-limit threshold is adjustable. Connect a
resistive divider between REF, the current-limit setting
input (LIM), and GND to set the current-limit threshold.
Alternatively, externally drive LIM (not to exceed 3.65V)
to set the current-limit threshold (see the Current-Limit
Threshold Selection section).
The short-circuit current threshold depends on the value
of the sense resistor and is calculated as follows:
where A
fier and is equal to 26V/V and R
tor value.
BLANK
RETRY
) has elapsed.
V
is the gain of the internal current-sense ampli-
) starts immediately after the blanking time
RETRY
SC
I
), the t
SC
, the switch turns on again while
=
Short Circuit and Current Limit
R
BLANK
SENSE
BLANK
1.3V
SENSE
×
timer begins counting.
, SC asserts low and
A
BLANK
V
is the sense resis-
BLANK
. During retry
, a retry