MAXIM MAX16948AGTE/V

19-6054; Rev 1; 4/12
EVALUATION KIT AVAILABLE
MAX16948
Automotive Dual Remote Antenna
Current-Sense LDO/Switch
General Description
The MAX16948 is a dual high-voltage, current-sensing low
dropout linear regulator (LDO)/switch designed to operate
with an input voltage range from 4.5V to 28V (45V load
dump tolerant). The device provides phantom power over
coax cable to remote radio frequency low-noise amplifiers
(LNAs) in automotive systems with a maximum current of
300mA per channel. The device also provides a fixed regulated output voltage of 8.5V or an adjustable 1V to 12.5V output voltage. The device can also be configured as a switch.
The device monitors the load current and provides an analog output current proportional to the sensed load current.
Accurate internal current limits pro­
tect the input supply
against both overcurrent and short-circuit conditions. The
device features an open-drain error output for each channel to
indicate to the microcontroller (FC) when a fault has occurred.
The device features short-to-battery protection to latch off the
internal LDO/switch during a short-to-battery event. During a
thermal overload, the device reduces power dissipa­tion by
going into thermal shutdown. It includes two independent
active-low, high-voltage-compatible shutdown inputs to
place each channel in a low-power shutdown mode.
The device is available in a 16-pin TQFN package with
exposed pad, a 16-pin QSOP package with exposed
pad, or a 16-pin QSOP package and is fully specified
over the -40NC to +105NC temperature range.
Features
S2-Channel LDO/Switch with Precision-Adjustable
Current-Sense (Up to 300mA Per Channel)
SWide Input Voltage Range: 4.5V to 28V (45V Load
Dump Tolerant)
SOn/Off Switching or Regulation of Phantom Power
Under µC Control
SReverse Current Protection
SOutput Short-to-Battery Protection
SLoad Current Monitoring to Detect Open-Load/
Normal/Short-Circuit Conditions
SOpen-Drain Error Status Signaling to µC
SInput Overvoltage Shutdown
SHigh Power-Supply Rejection Ratio (73dB)
Applications
Remote LNA Phantom Power
Automotive Camera and Sensor Power
Ordering Information appears at end of data sheet.
For related parts and recommended products to use with this part,
refer to www.maxim-ic.com/MAX16948.related.
Typical Operating Circuits
BATTERY INPUT
DIN
CIN1
µC SUPPLY
CIN2
IN
RPU1
LOUT1
R11
ERR1
ERROR FLAGS
REG
CURRENT-SENSE
OUTPUTS TO ADC
COUT1
DOUT1
RLOAD1
CLOAD2
RLOAD2
R21
LIM1
CLIM1
CSENSE1
RLIM2
LOUT2
CABLE2
LLOAD2
OUT2
SENSE2
RSENSE2
CLOAD1
MAX16948
SENSE1
RSENSE1
LLOAD1
FB1
ERR2
CREG
CABLE1
OUT1
RPU2
R12
CSENSE2
COUT2
DOUT2
FB2
OFF ON
R22
SHDN1
SHDN2
GND
LIM2
CLIM2
RLIM2
Typical Operating Circuits continued at end of data sheet.
����������������������������������������������������������������� Maxim Integrated Products 1
For pricing, delivery, and ordering information, please contact Maxim Direct at 1-888-629-4642,
or visit Maxim’s website at www.maxim-ic.com.
MAX16948
Automotive Dual Remote Antenna
Current-Sense LDO/Switch
ABSOLUTE MAXIMUM RATINGS
(All voltages referenced to GND.)
IN, SHDN1, SHDN2................................................-0.3V to +45V
ERR1, ERR2, REG................................................ -0.3V to +6.0V
FB1, FB2, SENSE1, SENSE2, LIM1, LIM2... -0.3V to (VREG + 0.3V)
OUT1, OUT2...........................................................-0.3V to +20V
Continuous Power Dissipation (TA = +70NC)
TQFN-EP (derate 25.0mW/NC above +70NC).............2000mW
QSOP-EP (derate 22.7mW/NC above +70NC)............1818mW
QSOP (derate 9.5mW/NC above +70NC)......................762mW
Operating Temperature Range........................ -40NC to +105NC
Storage Temperature Range............................ -65NC to +150NC
Junction Temperature......................................................+150NC
Lead Temperature (soldering, 10s).................................+300NC
Soldering Temperature (reflow).......................................+260NC
PACKAGE THERMAL CHARACTERISTICS (Note 1)
TQFN-EP
Junction-to-Ambient Thermal Resistance (BJA)...........40NC/W
Junction-to-Case Thermal Resistance (BJC)..................6NC/W
16 QSOP-EP
Junction-to-Ambient Thermal Resistance (BJA)...........44NC/W
Junction-to-Case Thermal Resistance (BJC)..................6NC/W
16 QSOP
Junction-to-Ambient Thermal Resistance (BJA).........105NC/W
Junction-to-Case Thermal Resistance (BJC)................37NC/W
Note 1: Package thermal resistances were obtained using the method described in JEDEC specification JESD51-7, using a fourlayer board. For detailed information on package thermal considerations, refer to www.maxim-ic.com/thermal-tutorial.
Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to absolute
maximum rating conditions for extended periods may affect device reliability.
ELECTRICAL CHARACTERISTICS
(VIN = 14V, TA = TJ = -40NC to +105NC, unless otherwise noted. Typical values are at TA = TJ = +25NC.) (Note 2)
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
4.5
28
UNITS
POWER SWITCH/LDO
Over 19V, output and current sense is
switched off (Note 3)
IN Operating Supply Range
VIN
IN Supply Current in Operation
IIN
VSHDN1/SHDN2 > 2.8V, TA = +25NC
IN Supply Current in Shutdown
ISD
SHDN1 = SHDN2 = GND, TA = +25NC,
VIN = 12V
Output switched off, for < 1s (Note 3)
IN Undervoltage Lockout
VUVL
IN Undervoltage Lockout
Hysteresis
VUVL-HYS
Voltage Drop of Internal Switch
VIN - VOUT1/OUT2
VFB
45
3.4
mA
7
FA
4.8
3.8
4.45
390
Measured between IN and OUT1/OUT2,
IOUT1/OUT2 = 100mA, FB1/FB2 = GND,
SW operation VIN R 5V, TA = +105NC
(Note 4)
For LDO mode with external resistive
dividers, IOUT1/OUT2_= 5mA to 150mA
V
mV
0.3V
V
Measured between IN and OUT1/OUT2,
IOUT1/OUT2 = 100mA, FB1/FB2 = GND,
SW operation VIN R 5V, TA = +25NC
Feedback Voltage
2.1
VIN rising
VIN falling
V
0.97
0.145
0.220
1
1.03
V
����������������������������������������������������������������� Maxim Integrated Products 2
MAX16948
Automotive Dual Remote Antenna
Current-Sense LDO/Switch
ELECTRICAL CHARACTERISTICS (continued)
(VIN = 14V, TA = TJ = -40NC to +105NC, unless otherwise noted. Typical values are at TA = TJ = +25NC.) (Note 2)
PARAMETER
Input Bias Current to FB1 and
FB2
SYMBOL
IFB1/FB2
CONDITIONS
VFB1/FB2 = 1.0V, LDO mode,
TA = +25NC
Feedback Threshold for
Internal Feedback Resistive
Divider
VFB1/FB2,TH
Switching to LDO mode with internal
8.5V resistive dividers
Adjustable Output Voltage
Range
VOUT1/OUT2
LDO mode with external resistive
dividers (Notes 3, 5)
FB1 and FB2 Load Regulation
DVFB, LOAD
VIN - VOUT1/OUT2 R 2V,
IOUT1/OUT2 = 5mA to 250mA,
LDO mode (Note 3)
FB1 and FB2 Line Regulation
DVFB, LINE
VIN - VOUT1/OUT2 R 2V,
IOUT1/OUT2 = 50mA, LDO mode (Note 3)
VOUT1/OUT2, 8.5V
IOUT1/OUT2 = 70mA, LDO mode with
internal resistive divider, 9V < VIN < 18V
Fixed Output Voltage 8.5V
Power-Supply Rejection Ratio
PSRR
MIN
MAX
UNITS
-0.5
+0.5
FA
VREG 1.7
VREG 0.8
V
1
12.5
V
8.33
VIN - VOUT1/OUT2 R 2V,
IOUT1/OUT2 = 10mA at f = 100Hz,
LDO mode VOUT1/OUT2 = 8.5V,
VRIPPLE = 0.5VP-P (Note 3)
TYP
-7
mV
100
FV/V
8.5
8.67
73
V
dB
CURRENT SENSE
SENSE1 to OUT1 and SENSE2
to OUT2 Current Ratio
SENSE1, SENSE2, LIM1, LIM2
Leakage Current
AI
ILEAK
VSENSE1/SENSE2
< 3V
IOUT1/OUT2 = 100mA,
VIN = 5V, 19V
0.485
0.5
0.515
50mA P IOUT1/OUT2
P 300mA, VIN R 5V
(Note 3)
0.45
0.5
0.55
20mA P IOUT1/OUT2 P
50mA, VIN R 5V
(Note 3)
0.415
0.5
0.585
5mA P IOUT1/OUT2 P
20mA, VIN R 5V
(Note 3)
0.325
0.5
0.675
%
SHDN1 = SHDN2 = GND, TA =+ 25NC
2
FA
FAILURE DETECTION
LIM1 and LIM2 Current-Limit
Threshold Voltage
VLIM1/LIM2,TH
Voltage on LIM1 and LIM2 for which
output current is limited
2.375
2.5
2.625
V
21
23
V
IN Overvoltage Lockout
Threshold (Rising)
VOVLO,R
VIN rising
19
IN Overvoltage Lockout
Threshold (Falling)
VOVLO,F
VIN falling
18.5
IN Overvoltage Lockout
Hysteresis
VOVLO,H
V
600
mV
����������������������������������������������������������������� Maxim Integrated Products 3
MAX16948
Automotive Dual Remote Antenna
Current-Sense LDO/Switch
ELECTRICAL CHARACTERISTICS (continued)
(VIN = 14V, TA = TJ = -40NC to +105NC, unless otherwise noted. Typical values are at TA = TJ = +25NC.) (Note 2)
PARAMETER
Short-to-BAT Threshold in Off
State
Reverse Current Detection
Level
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
VS2B
VOUT1/OUT2 - VIN, checked during turnon sequence
-500
-80
+110
mV
Power FET on (SW or LDO mode)
-100
-50
-1
mA
4.16
20
Fs
IREVCUR
tPD-RC
Delay to shutdown the switch or LDO
after drop over RON becomes negative,
IOUT1/OUT2 = -200mA (typ), TA = +25NC
Reverse Current Blanking Time
tBLK-RC
Blanking time for reverse current and
FB1/FB2 out of range after rising edge
of SHDN1, SHDN2, or current limiting
event is over
Feedback Voltage Out of
Range
VFBERR
LDO mode, internal pulldown resistor
switched on, FB rising
Feedback Voltage Out-ofRange Hysteresis
VFBERR-HYS
LDO mode, internal pulldown resistor
switched on (Note 3)
Reverse Current (Short-to-BAT)
Shutdown Delay
16
1.12
ms
1.15
1.28
V
39
100
mV
OVERTEMPERATURE PROTECTION (Note 3)
Thermal Shutdown
Thermal Shutdown Hysteresis
TSHDN
160
NC
TSHDN-HYS
15
NC
SUPPORTING CIRCUITS, INTERFACE SIGNALS
Internal Voltage Regulator
VREG
TA = +25NC, IREG = 0mA,
VIN = 4.5V to 18V
4
5
5.5
V
TA = +25NC, IREG = 0mA,
VIN = 6.5V to 18V
4.5
5
5.5
V
15
Internal Voltage Regulator
Current Limit
IREG
(Note 4)
ERR1 and ERR2 OutputVoltage Low
VOL
Sinking current = 10mA
ERR1 and ERR2 Open-Drain
Leakage Current
ERR1 and ERR2 not asserted, VERR1/
ERR2 = 5V, TA = +25NC
SHDN1 and SHDN2 High
VSHDN1/SHDN2,HI
SHDN1 and SHDN2 Low
VSHDN1/SHDN2,LO
SHDN1 and SHDN2 Pulldown
Resistance
RSHDN
Startup Response Time
tST
OUT Pulldown Resistor
ROUT1/OUT2-OFF
Note
Note
Note
Note
mA
0.4
V
1
FA
2.8
V
0.8
V
VSHDN1/SHDN2 = 2V
500
kI
SHDN1 and SHDN2 rising to turn on
LDO/switch (Note 3)
300
Fs
SHDN1 = SHDN2 = GND
56
kI
2: Devices are tested at TA = +25NC and guaranteed by design for TA = TMIN to TMAX.
3: Guaranteed by design; not production tested.
4: Guaranteed by ATE characterization. Limits are not production tested.
5: In case of OUT1/OUT2 shorted to BAT, feedback network must protect FB1/FB2 from violating their absolute maximum ratings. For OUT1/OUT2 set below 3.3V, use an additional 5V clamp on FB1/FB2 with low parasitic capacitance.
����������������������������������������������������������������� Maxim Integrated Products 4
MAX16948
Automotive Dual Remote Antenna
Current-Sense LDO/Switch
Typical Operating Characteristics
(VIN = 14V, TA = +25NC, see the Typical Operating Circuits, unless otherwise noted.)
SHDN1 = SHDN2 = GND
6.5
FB_ = GND
600
500
6.0
VIN - VOUT (mV)
5.5
5.0
TA = +105°C
400
TA = +25°C
300
200
4.5
100
TA = -40°C
0
4.0
-20
5
30
55
80
50
0
105
100
DROPOUT VOLTAGE vs. OUTPUT CURRENT
DROPOUT VOLTAGE (mV)
500
TA = +105°C
400
TA = +25°C
300
200
100
300
FB_ = REG
500
TA = +105°C
400
TA = +25°C
300
200
100
TA = -40°C
0
TA = -40°C
0
0
50
100
150
200
250
300
50
0
100
150
200
250
300
OUTPUT CURRENT (mA)
OUTPUT CURRENT (mA)
VOLTAGE DROP OF INTERNAL SWITCH
vs. SUPPLY VOLTAGE
POWER-SUPPLY REJECTION RATIO
vs. FREQUENCY
FB_ = GND
IOUT_ = 5mA
7.9
0
MAX16948 toc05
8.0
7.8
7.7
-10
-20
-30
OUT1
7.6
PSRR (dB)
VIN - VOUT (mV)
250
600
DROPOUT VOLTAGE (mV)
VOUT = 5V
FB_ = EXTERNAL
600
200
DROPOUT VOLTAGE vs. OUTPUT CURRENT
700
MAX16948 toc03
700
150
OUTPUT CURRENT (mA)
TEMPERATURE (°C)
MAX16948 toc04
-45
7.5
7.4
7.3
VOUT_ = 5V
FB_ = EXTERNAL RESISTIVE DIVIDER
VRIPPLE_ = 0.5VP-P
IOUT_ = 10mA
MAX16948 toc06
SHUTDOWN CURRENT (µA)
700
MAX16948 toc01
7.0
MAX16948 toc02
VOLTAGE DROP OF INTERNAL SWITCH
vs. OUTPUT CURRENT
SHUTDOWN CURRENT vs. TEMPERATURE
-40
-50
-60
-70
OUT2
-80
7.2
7.1
-90
7.0
-100
0
5
10
SUPPLY VOLTAGE (V)
15
20
0.01
1
100
10,000
FREQUENCY (kHz)
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MAX16948
Automotive Dual Remote Antenna
Current-Sense LDO/Switch
Typical Operating Characteristics (continued)
(VIN = 14V, TA = +25NC, see the Typical Operating Circuits, unless otherwise noted.)
POWER-UP WAVEFORM
(FB_ = REG, IOUT_ = 90mA)
POWER-SUPPLY REJECTION RATIO
vs. FREQUENCY
-10
-20
MAX16948 toc08
MAX16948 toc07
0
FB_ = REG
VRIPPLE_ = 0.5VP-P
IOUT_ = 10mA
VIN
10V/div
VOUT1
5V/div
-40
-50
VOUT2
5V/div
-60
-70
-80
-90
0.01
1
100
100µs/div
10,000
FREQUENCY (kHz)
POWER-UP WAVEFORM
(FB_ = GND, IOUT_ = 90mA)
STARTUP WAVEFORM
(FB_ = REG, IOUT_ = 90mA)
MAX16948 toc09
MAX16948 toc10
VIN
10V/div
VSHDN1 AND VSHDN2
5V/div
VOUT1
10V/div
VOUT1
5V/div
VOUT2
10V/div
VOUT2
5V/div
100µs/div
STARTUP WAVEFORM
(FB_ = GND, IOUT_ = 90mA)
CURRENT-SENSE AMPLIFIER GAIN
vs. TEMPERATURE
MAX16948 toc11
0.504
VSHDN1 AND VSHDN2
5V/div
VOUT1
10V/div
VOUT2
10V/div
200µs/div
0.502
MAX16948 toc12
200µs/div
CURRENT-SENSE AMPLIFIER GAIN (%)
PSRR (dB)
-30
FB_ = GND
IOUT_ = 100mA
0.500
0.498
SENSE2
0.496
SENSE1
0.494
0.492
-45
-20
5
30
55
80
105
TEMPERATURE (°C)
����������������������������������������������������������������� Maxim Integrated Products 6
MAX16948
Automotive Dual Remote Antenna
Current-Sense LDO/Switch
Typical Operating Characteristics (continued)
(VIN = 14V, TA = +25NC, see the Typical Operating Circuits, unless otherwise noted.)
CURRENT-SENSE AMPLIFIER GAIN
vs. OUTPUT CURRENT
CURRENT-SENSE AMPLIFIER ERROR
vs. OUTPUT CURRENT
0.501
SENSE2
0.500
0.499
0.498
0.497
SENSE1
0.496
0.495
0.494
0.493
0.6
FB = GND
0.492
0
50
100
150
200
250
MAX16948 toc14
0.502
CURRENT-SENSE AMPLIFIER ERROR (%)
MAX16948 toc13
CURRENT-SENSE AMPLIFIER GAIN (%)
0.503
0.4
0.2
0
SENSE2
-0.2
-0.4
-0.6
SENSE1
-0.8
-1.0
-1.2
-1.4
FB = GND
-1.6
300
0
OUTPUT CURRENT (mA)
50
100
VSENSE_ vs. RSENSE_
300
MAX16948 toc16
4.0
5.0
4.5
3.5
4.0
3.0
VREG (V)
VSENSE_ (V)
250
VREG vs. IREG
FB_ = GND
IOUT_ = 300mA
4.5
200
5.5
MAX16948 toc15
5.0
150
OUTPUT CURRENT (mA)
2.5
2.0
3.5
3.0
2.5
1.5
1.0
2.0
0.5
1.5
0
1.0
0
1
2
3
4
0
10
20
30
40
RSENSE_ (kΩ)
IREG (mA)
LINE TRANSIENT
(FB_ = REG, IOUT_ = 50mA)
LINE TRANSIENT
(VOUT_ = 5V, IOUT_ = 50mA)
MAX16948 toc17
18V
MAX16948 toc18
VIN
10V/div
10V
1ms/div
18V
VIN
10V/div
10V
VOUT1
(AC-COUPLED)
10mV/div
VOUT1
(AC-COUPLED)
10mV/div
VOUT2
(AC-COUPLED)
10mV/div
VOUT2
(AC-COUPLED)
10mV/div
1ms/div
����������������������������������������������������������������� Maxim Integrated Products 7
MAX16948
Automotive Dual Remote Antenna
Current-Sense LDO/Switch
15 LIM1
SENSE2
12
11
10
9
LIM1 13
8
LIM2
7
FB2
6
REG
5
GND
14 SENSE1
FB1 14
IN 4
13 ERR1
SHDN2 5
12 ERR2
N.C. 15
OUT1 16
11 SENSE2
OUT2 6
GND 7
10 LIM2
REG 8
9
MAX16948
*EP
+
1
SHDN1
*EP
FB2
QSOP-EP/QSOP
2
3
4
OUT2
SHDN1 3
ERR2
16 FB1
MAX16948
SHDN2
OUT1 2
+
IN
N.C. 1
TOP VIEW
ERR1
TOP VIEW
SENSE1
Pin Configurations
TQFN
(4mm × 4mm)
*CONNECT EP TO GND.
Pin Descriptions
PIN
NAME
FUNCTION
QSOP/
QSOP-EP
TQFN-EP
1
15
N.C.
2
16
OUT1
LDO/Switch Output 1 to Remote Load. Bypass OUT1 to GND with >1FF in parallel with
100nF low-ESR ceramic capacitors for regulator stability.
3
1
SHDN1
Active-Low Shutdown Input for OUT1. SHDN1 is pulled to GND with an internal 500kI
resistor.
4
2
IN
5
3
SHDN2
6
4
OUT2
LDO/Switch Output 2 to remote load. Bypass OUT2 to GND with >1FF in parallel with 100nF
low-ESR ceramic capacitors for regulator stability.
7
5
GND
Ground
8
6
REG
Internal 5V Regulator. Provides supply for internal low-voltage blocks, SENSE_, and LIM_
outputs.
FB2
Feedback Input for Setting the OUT2 Voltage. Connect FB2 to GND to select current-limited
switch operation. Connect to an external resistive divider for adjustable output-voltage
operation. Connect FB2 to REG to choose the internal resistive divider for the 8.5V regulator
option.
9
7
No Connection. Not internally connected.
Input Voltage. Bypass IN to GND with an electrolytic capacitor with a minimum value of 10FF
and a low-ESR ceramic capacitor with a minimum value of 0.1FF.
Active-Low Shutdown Input for OUT2. SHDN2 is pulled to GND with an internal 500kI
resistor.
����������������������������������������������������������������� Maxim Integrated Products 8
MAX16948
Automotive Dual Remote Antenna
Current-Sense LDO/Switch
Pin Descriptions (continued)
PIN
QSOP/
QSOP-EP
TQFN-EP
NAME
LIM2
FUNCTION
Output of Current Sense for Limiting. This output is proportional to current flowing through
OUT2. The internal current-limit amplifier is tripped when the voltage on LIM2 reaches 2.5V.
Connect a resistor to GND to set the level for current limitation and a 0.1FF capacitor in parallel for frequency compensation of the current-limit loop.
10
8
11
9
SENSE2
12
10
ERR2
Open-Drain Fault Indicator Output 2
13
11
ERR1
Open-Drain Fault Indicator Output 1
14
12
SENSE1
15
13
Output of Current Sense for Sensing. The current of SENSE2 is proportional to the current
flowing through OUT2. Connect a resistor from SENSE2 to GND to set the output voltage
level. Additionally, connect a 0.1FF capacitor from SENSE2 to GND.
Output of Current Sense for Sensing. The current of SENSE1 is proportional to the current
flowing through OUT1. Connect a resistor from SENSE1 to GND to set the output voltage
level. Additionally, connect a 0.1FF capacitor from SENSE1 to GND.
LIM1
Output of Current Sense for Limiting. This output is proportional to current flowing through
OUT1. The internal current-limit amplifier is tripped when the voltage on LIM1 reaches 2.5V.
Connect a resistor to GND to set the level for current limitation and a 0.1FF capacitor in parallel for frequency compensation of the current-limit loop.
16
14
FB1
Feedback Input for Setting the OUT1 Voltage. Connect FB1 to GND to select current-limited
switch operation. Connect to an external resistive divider for adjustable output-voltage
operation. Connect FB1 to REG to choose the internal resistive divider for the 8.5V regulator
option.
—
—
EP
Exposed Pad (MAX16948A only). Connect EP to the ground plane for optimal heat dissipation. Do not use EP as the primary electrical ground connection.
����������������������������������������������������������������� Maxim Integrated Products 9
MAX16948
Automotive Dual Remote Antenna
Current-Sense LDO/Switch
Functional Diagram
2x
OUT1/
OUT2
IN
I-SENSE
CHARGE
PUMP
REF
I-LIM (2.5V)
FB (1.0V)
CURRENT
LIMIT
REVERSE I
DIAGNOSTICS
OUT > IN
FB > 1.2V
FB1/
FB2
SHDN1
OUT_ > IN_
SHDN2
CONTROL
FB_ > 110%
ERR1
ERR2
IN
CURRENT
SOURCES
TEMPERATURE
SENSOR
21V
REF,
REG
REG
MAX16948
LIM1/
LIM2
SENSE1
SENSE2
Detailed Description
The MAX16948 is a dual high-voltage, current-sensing
LDO/switch designed to operate with an input voltage
range from 4.5V to 28V (45V load dump tolerant). The
device provides phantom power over coax cable to
remote radio frequency low-noise amplifiers (LNAs) in
automotive systems with a maximum current of 300mA
per channel. The device also provides a fixed regulated
output voltage of 8.5V, an adjustable 1V to 12.5V output
voltage, or the device can be configured as a switch. The
device is ideal for providing phantom power to remote
radio-frequency LNAs in automotive applications.
GND
The device monitors the load current, and its currentsense outputs provide a current proportional to the
sensed load current. An accurate programmable current
limit pro­
tects the input supply against both overcurrent and short-circuit conditions. The device features
open-drain fault indicator outputs and overtemperature
shutdown.
The device features short-to-battery protection to latch off
the internal LDO/switch during a short-to-battery event.
During a thermal overload, the device reduces power
dissipa­tion by going into thermal shutdown. It includes
dual independent, active-low, high-voltage-compatible
shutdown inputs to place each channel in a low-power
shutdown mode.
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MAX16948
Automotive Dual Remote Antenna
Current-Sense LDO/Switch
Fault Detection
The device monitors the load current through an internal
sense resistor to protect against short-circuit, short-tobattery, and reverse current faults. In addition, the device
also detects input and output overvoltage conditions and
features thermal shutdown.
Short Circuit and Overcurrent
The current limit of each channel is programmed with
an external resistor connected to the output of the current sense amplifiers LIM_ to protect the device during
short-circuit or overcurrent conditions. When the voltage
at LIM_ reaches the internal 2.5V threshold, the output
current of the LDO/switch is limited, and ERR_ asserts
low but the output is not disabled. The ERR_ and LIM_
outputs should be monitored by the FC, and the channel
experiencing the short-circuit or overcurrent condition
should be disabled by pulling SHDN_ low. If this condition persists, thermal shutdown could occur and both
outputs could be disabled.
Short-to-Battery and Reverse Current Detection
It is possible for OUT_ to be shorted to the battery due
to a fault in the system. Each channel detects this failure
by comparing the voltage at OUT_ and IN before the
switch turns on. Every time the LDO/switch is enabled on
the rising edge of SHDN_ or during the exiting of thermal
shutdown, the short-to-battery detec­tion is performed. At
this point, if the device detects the short-to-battery fault,
the LDO/switch stays off and ERR_ is asserted low. The
fault is latched, and the startup resumes when the shortto-battery fault is removed and SHDN_ is toggled.
During normal operation if a short-to-battery fault results
in reverse current for more than 5Fs (typ) the LDO/switch
is latched off and ERR_ is asserted low. To remove the
latched condition after a short-to-battery (reverse current)
fault, the fault condition must first be removed and SHDN_
must be toggled.
Series inductance and the output capacitor can produce
ringing during large load transients when enabling the
LDO/switch, resulting in an output voltage that temporarily
exceeds the input volt­age. Blanking is implemented during
startup. The reverse current blank­ing time (tREV_BLANK) is
16ms (typ).
When the MAX16948 is operated with input voltage close
to the output voltage, as in switch mode operation or LDO
mode in dropout, care must be taken to avoid a false
reverse current detection in the presence of a short circuit
to ground fault. If both channels are enabled and one channel is shorted to ground after startup, the current drawn
from CIN may result in a temporary dip in the intput voltage,
which may trigger the reverse current detection fault. To
aovoid this false trigger event, use an electrolytic capacitor
of at least 100FF.
Thermal Shutdown
Thermal shutdown circuitry protects the device from
overheating. The switch turns off immediately when the
junction temperature exceeds +160NC (typ). The switch
turns on again after the device tempera­ture drops by
approximately 15NC (typ).
FB Inputs (FB1/FB2)
FB1 and FB2 control the output voltage on OUT1 and
OUT2. Connect FB_ to GND to select current-limited
switch operation. Connect to an external resistive divider
for adjustable output voltage operation (feedback voltage 1V (typ)). Connect FB_ to REG to choose the internal
resistive divider for the 8.5V regulator option.
Table 1. Fault Response
DEVICE STATUS
VLIM_(V)
VERR
LDO/SW OUTPUT
LATCHED
Normal Operation
0 P VLIM_< 2.5
High
Enabled
No
Short Circuit to GND or
Overcurrent
2.5
Low
Enabled
No
VOUT > VIN at Startup
0
Low
Disabled
Yes
Reverse Current
0
Low
Disabled
Yes
VFB > 1.2V
0
High
Enabled
No
Input Overvoltage
0
Low
Disabled
No
Thermal Shutdown
0
High
Disabled
No
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MAX16948
Automotive Dual Remote Antenna
Current-Sense LDO/Switch
Undervoltage and Overvoltage Lockout
The device includes undervoltage lockout circuitry
(UVLO) to prevent erroneous switch operation when the
input voltage goes below 4.45V (max) during startup and
brownout conditions. Input voltages of less than 4.45V
inhibit operation of the device by turning off the internal
charge pump and the switch.
The device also features an overvoltage lockout (OVLO)
threshold of +21V (typ). When VIN is greater than VOVLO,
the device immediately turns off the switch and the internal charge pump.
Shutdown (SHDN1, SHDN2)
The device features two active-low shut­
down inputs
(SHDN1, SHDN2) to place the device in a low-power
shutdown mode. SHDN1 controls OUT1 and SHDN2
controls OUT2. The device turns off both channels and
consumes a maximum of 7FA (at VIN = 12V) of shutdown
current when both SHDN1 and SHDN2 are low. Driving
SHDN1 and/or SHDN2 high initiates device turn-on with
short-to-battery detection. SHDN1 and SHDN2 are pulled
to GND with an internal 500kI resistor.
Internal Voltage Regulator (REG)
The device features an internal regulator that regulates
the input voltage to +5V to power all inter­nal circuitry.
Bypass the regulator output (REG) to GND with a 1FF
ceramic capacitor. The REG output can be used to supply external circuitry up to a maximum 15mA current.
Applications Information/External
Component Selection
Fixed/Adjustable Output Voltage
The device is configurable to provide a fixed 8.5V output
or as an adjustable LDO with an output between 1V and
12.5V. Connect FB_ to REG to configure the device as
an 8.5V LDO. Connect a resistive divider between OUT_,
FB_, and GND to set the output to the desired voltage.
FB_ is regulated to 1.0V with Q3% accuracy for a load
current between 5mA and 150mA. Select a value for R2
and calculate R1 as follows:
V

=
R1  OUT_ − 1R2
 V

 FB_

where R2 must be less than or equal to 1kI. Select R1
and R2 such that the maximum input bias current at FB
(±0.5FA) is negligible compared to the current flowing
through R1 and R2.
Current-Limit Resistor and
Capacitor Selection
The current-sense outputs at LIM1/LIM2 are proportional
to the load current at OUT1/OUT2 and are internally connected to a current-limit comparator referenced to 2.5V.
The desired current limit is set with an external resistor
RLIM_using the following equation:
2.5(V)
R LIM_(Ω) =
0.5% × ILOAD_MAX(A)
A 0.1FF compensation capacitor CLIM_ must be placed
in parallel with RLIM_ to establish a dominant pole in the
current limiting loop to maintain stability and to prevent
fast current transients from prematurely triggering the
current limit.
Current-Sense Resistor Selection
The current-sense outputs SENSE1/SENSE2 are proportional to the load current at OUT1/OUT2. An output
resistor RSENSE_ must be connected between SENSE1/
SENSE2 and GND to generate a current-sense voltage
prior to sampling by an ADC. RSENSE is calculated using
the following equation:
VADC,FS (V)
R SENSE_ (Ω) =
0.5% × ILOAD_MAX(A)
where VADC,FS is the full-scale input voltage of the ADC. A
0.1FF capacitor CSENSE should be placed in parallel with
RSENSE to hold the voltage during ADC sampling cycles.
In addition to ADC sampling, open-load or overcurrent
conditions can be detected by using external comparators
and splitting RSENSE_ into a resistive divider as shown in
Figure 1. In this circuit the outputs of comparators U1 and
SENSE_
R3
MAX16948
R4
VOC,TH
U1
VOC
U2
VOL
VOL,TH
R5
Figure 1. Open-Load and Overcurrent Detection Circuit
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MAX16948
Automotive Dual Remote Antenna
Current-Sense LDO/Switch
Table 2. Open-Load and OvercurrentDetection Circuit States
OC
OL
STATE
0
0
Normal Operation
0
1
Open-Load Condition
1
0
Overcurrent Condition
1
1
Invalid State
U2 indicate the operating state of the circuit as shown in
Table 2.
The open-load and overcurrent limits are set using the
following equations:
VOL,TH (V)
R5(Ω) =
0.5% × I OPEN−LOAD(A)
where VOL,TH is the open-load voltage threshold for
comparator U2 and IOPEN-LOAD is the desired open-load
threshold for the current flowing through the LDO/switch.
=
R4(Ω)
VOC,TH (V)
0.5% × I OVERCURRENT(A)
− R5
where VOC,TH is the overcurrent voltage threshold for
comparator U1. IOVERCURRENT is the desired overcurrent threshold for the current flowing through the LDO/
switch and the internal current limit should be programmed such that ILOAD_MAX > IOVERCURRENT.
Input Capacitor
Connect a parallel electrolytic capacitor and a low-ESR
ceramic capacitor from IN to GND to limit the inputvoltage drop during momentary output short-circuit conditions and to protect the device against transients due
to inductance on the IN line. For example, use at least a
0.1FF ceramic capacitor in parallel with a 10FF electrolytic capactior if the input inductance (including any stray
inductance) is estimated to be 20FH. Larger capacitor
values reduce the voltage undershoot and overshoot in
case of reverse current.
Output Capacitor
Connect >1FF in parallel with 0.1FF low-ESR ceramic
capacitors between OUT1/OUT2 and GND for regulator
stability. These capacitors should be placed as close to
the device as possible. Utilize capacitors with an X7R
dielectric to ensure stability over the operating temperature range of the device.
In an analogous fashion to the input capacitor, an output
capacitor protects the device against transients due to
any series inductance in the output. Under no condi­tions
should the voltage on OUT1/OUT2 go below -0.3V as
specified in the Absolute Maximum Ratings section. A
Schottky diode is required as a clamp if transients are
expected to go below ground.
R3(Ω) = RSENSE_ - R4 - R5
The open-load voltage threshold VOL,TH and overcurrent
threshold VOC,TH can be generated from REG utilizing a
resistive divider. The thresholds should be selected such
that VOC,TH > VOL,TH.
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MAX16948
Automotive Dual Remote Antenna
Current-Sense LDO/Switch
Typical Operating Circuits (continued)
BATTERY INPUT
10µF
0.1µF
1µF
µC SUPPLY
IN
2.7kΩ
REG
1mH
2.7kΩ
LLOAD1
1µF
ERR1
ERROR FLAGS
CABLE1
OUT1
CLOAD1
RLOAD1
CLOAD2
RLOAD2
FB1
ERR2
MAX16948
LIM1
SENSE1
4kΩ
0.1µF
0.1µF
2.5kΩ
CURRENT-SENSE
OUTPUTS TO ADC
1mH
SENSE2
4kΩ
CABLE2
LLOAD2
OUT2
3kΩ
0.1µF
1µF
FB2
750Ω
SHDN1
OFF ON
SHDN2
GND
LIM2
0.1µF
2.5kΩ
Ordering Information
PART
TEMP RANGE
PIN-PACKAGE
MAX16948AGTE/V+
-40NC to +105NC
16 TQFN-EP**
MAX16948AGEE/V+
-40NC to +105NC
16 QSOP-EP**
MAX16948BGEE/V+*
-40NC to +105NC
16 QSOP
/V denotes an automotive qualified part.
+Denotes a lead(Pb)-free/RoHS-compliant package.
*Future product—contact factory for availability.
**EP = Exposed pad.
Chip Information
Package Information
For the latest package outline information and land patterns
(footprints), go to www.maxim-ic.com/packages. Note that a
“+”, “#”, or “-” in the package code indicates RoHS status only.
Package drawings may show a different suffix character, but
the drawing pertains to the package regardless of RoHS status.
PACKAGE
TYPE
PACKAGE
CODE
OUTLINE
NO.
LAND
PATTERN NO.
16 TQFN-EP
T1644+4
21-0139
90-0070
16 QSOP-EP
E16E+9
21-0112
90-0240
16 QSOP
E16+5
21-0055
90-0167
PROCESS: BiCMOS
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MAX16948
Automotive Dual Remote Antenna
Current-Sense LDO/Switch
Revision History
REVISION
NUMBER
REVISION
DATE
0
9/11
Initial release
1
4/12
Updated maximum output voltage
DESCRIPTION
PAGES
CHANGED
—
1, 3, 10, 12
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Maxim reserves the right to change the circuitry and specifications without notice at any time.
Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600
© 2012
Maxim Integrated Products 15
Maxim is a registered trademark of Maxim Integrated Products, Inc.