2MHz, High-Brightness LED Drivers MAX16832A/MAX16832C with Integrated MOSFET and High-Side Current Sense

2MHz, High-Brightness LED Drivers MAX16832A/MAX16832C with Integrated MOSFET and High-Side Current Sense
EVALUATION KIT AVAILABLE
MAX16832A/MAX16832C
2MHz, High-Brightness LED Drivers
with Integrated MOSFET and
High-Side Current Sense
General Description
Benefits and Features
The MAX16832A/MAX16832C step-down constant-current high-brightness LED (HB LED) drivers provide a
cost-effective design solution for automotive
interior/exterior lighting, architectural and ambient lighting, LED bulbs, and other LED illumination applications.
The MAX16832A/MAX16832C operate from a +6.5V to
+65V input voltage range and can provide an output
current up to 700mA, if operated up to a temperature of
+125°C, or up to a 1A if operated up to a temperature
of +105°C. A high-side current-sense resistor adjusts
the output current, and a dedicated pulse-width modulation (PWM) input enables pulsed LED dimming over a
wide range of brightness levels.
• Cost-Effective Solution for a Wide Range of LED
Lighting Applications
• 6.5V to 65V Input Voltage Range
• Output Current Up to 1A
• ±3% LED Current Accuracy
• Selectable Dimming Options: Linear or PWM
These devices are well suited for applications requiring
a wide input voltage range. The high-side current sensing and an integrated current-setting circuitry minimize
the number of external components while delivering an
average output current with ±3% accuracy. A hysteretic
control method ensures excellent input supply rejection
and fast response during load transients and PWM dimming. The MAX16832A allows 10% current ripple, and
the MAX16832C allows 30% current ripple. Both
devices operate up to a 2MHz switching frequency,
thus allowing the use of small-sized components.
The MAX16832A/MAX16832C offer an analog dimming
feature that reduces the output current by applying an
external DC voltage below the internal 2V threshold voltage from TEMP_I to GND. TEMP_I also sources 25µA to
a negative temperature coefficient (NTC) thermistor connected between TEMP_I and GND, thus providing an
analog thermal-foldback feature that reduces the LED
current when the temperature of the LED string exceeds
a specified temperature point. Additional features
include thermal-shutdown protection.
The MAX16832A/MAX16832C operate over the -40°C to
+125°C automotive temperature range and are available
in a thermally enhanced 8-pin SO package.
• Minimal Component Count Saves Cost and Space
• On-Board 65V, 0.45Ω Power MOSFET
• Resistor-Programmable Constant LED Current
• Integrated High-Side Current Sense with 200mV
Current-Sense Reference
• Hysteretic Control: Up to 2MHz Switching
Frequency
• Protection Features and Wide Operating
Temperature Range Improves Lighting Fixture
Reliability
• Thermal-Foldback Protection Dims LEDs to
Minimize Overheating
• Thermal-Shutdown Protection
• Available in a Thermally Enhanced 8-Pin SO Package
• Operation over -40°C to +125°C Temperature Range
Ordering Information and Pin Configuration appear at end
of data sheet.
Typical Application Circuit
D1
HB LEDs
VIN
RSENSE
L1
C2
Applications
• Architectural, Industrial, and Ambient Lighting
1
• Automotive RCL, DRL, and Fog Lights
• Heads-Up Displays
• Indicator and Emergency Lighting
• PoE Powered Lighting
2
CS
TEMP_I
IN
DIM
C1
3
4
GND
PGND
MAX16832A
MAX16832C
LX
LX
8
7
NTC*
ON
OFF
6
5
*OPTIONAL
19-4140; Rev 7; 2/15
2MHz, High-Brightness LED Drivers
with Integrated MOSFET and
High-Side Current Sense
MAX16832A/MAX16832C
Absolute Maximum Ratings
IN, CS, LX, DIM to GND .........................................-0.3V to +70V
TEMP_I to GND .......................................................-0.3V to +6V
PGND to GND ......................................................-0.3V to +0.3V
CS to IN .................................................................-0.3V to +0.3V
Maximum Current into Any Pin
(except IN, LX, and PGND).............................................20mA
Continuous Power Dissipation (TA = +70°C)
8-Pin SO (derate 18.9mW/°C above +70°C)...........1509.4mW
Operating Temperature Range
700mA (max) Output Current ........................-40°C to +125°C
1A (max) Output Current ...............................-40°C to +105°C
Junction Temperature ......................................................+150°C
Storage Temperature Range .............................-65°C to +150°C
Soldering (reflow).............................................................+260°C
Lead Temperature (soldering, 10s) .................................+300°C
Pin-to-Pin ESD Ratings......................................................±2.5kV
Package Thermal Characteristics (Note 1)
SO-EP
Junction-to-Ambient Thermal Resistance (θJA)...............+53°C/W
Junction-to-Case Thermal Resistance (θJC)......................+5°C/W
Note 1: Package thermal resistances were obtained using the method described in JEDEC specification JESD51-7, using a four-layer
board. For detailed information on package thermal considerations, refer to www.maximintegrated.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 = +24V, VDIM = VIN, TA = TJ = -40°C to +125°C, unless otherwise noted. Typical values are at TA = +25°C.)
PARAMETER
SYMBOL
Input Voltage Range
CONDITIONS
VIN
MIN
TYP
6.5
MAX
UNITS
65
V
Ground Current
No switching
1.5
mA
Supply Current
VDIM < 0.6V, VIN = 12V
350
µA
VCS = VIN - 100mV, VIN rising until VLX <
0.5VIN
6.25
UNDERVOLTAGE LOCKOUT (UVLO)
Undervoltage Lockout
UVLO
6.5
V
VCS = VIN - 100mV, VIN falling until VLX >
0.5VIN
6.0
Undervoltage-Lockout Hysteresis
0.5
V
SENSE COMPARATOR
Sense Voltage Threshold High
Sense Voltage Threshold Low
2
VSNSHI
VSNSLO
MAX16832A, VIN - VCS rising from 140mV
until VLX > 0.5VIN, VDIM = 5V
197
205
213
MAX16832C, VIN - VCS rising from 140mV
until VLX > 0.5VIN, VDIM = 5V
218
230
236
MAX16832A, VIN - VCS falling from 260mV
until VLX < 0.5VIN , VDIM = 5V
185
190
198
MAX16832C, VIN - VCS falling from 260mV
until VLX < 0.5VIN, VDIM = 5V
166
mV
mV
170
180
Propagation Delay to Output High
tDPDH
Falling edge of VIN - VCS from 140mV to
260mV to VLX > 0.5VIN
50
ns
Propagation Delay to Output Low
tDPDL
Rising edge of VCS - VIN from 260mV to
140mV to VLX < 0.5VIN
50
ns
CS Input Current
ICSIN
VIN - VCS = 200mV, VIN = VCS
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3.5
µA
Maxim Integrated | 2
2MHz, High-Brightness LED Drivers
with Integrated MOSFET and
High-Side Current Sense
MAX16832A/MAX16832C
Electrical Characteristics (continued)
(VIN = +24V, VDIM = VIN, TA = TJ = -40°C to +125°C, unless otherwise noted. Typical values are at TA = +25°C.)
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
VIN = VDIM = 24V, VCS = 23.9V,
ILX = 700mA
0.45
0.9
VIN = VDIM = 6.0V, VCS = 5.9V,
ILX = 700mA
1
2
UNITS
INTERNAL MOSFET
Drain-to-Source Resistance
RDSON
LX Leakage Current
ILX_LEAK
Ω
VDIM = 0V, VLX = 65V
10
µA
DIM INPUT
DIM Input-Voltage High
VIH
VIN - VCS = 100mV
DIM Input-Voltage Low
VIL
VCS - VIN = 100mV
DIM Turn-On Time
tDIM_ON
2.8
V
0.6
V
VDIM rising edge to VLX < 0.5VIN
60
DIM Input Leakage High
VDIM = VIN
8
15
µA
DIM Input Leakage Low
VDIM = 0V
-1.5
0
µA
-3
ns
THERMAL SHUTDOWN
Thermal-Shutdown Threshold
Temperature rising
+165
o
C
10
o
C
Thermal-Shutdown Threshold
Hysteresis
THERMAL FOLDBACK
Thermal-Foldback Enable
Threshold Voltage
VTFB_ON
VDIM = 5V
Thermal-Foldback Slope
FBSLOPE
VDIM = 5V
TEMP_I Output Bias Current
ITEMP_I
1.9
2.0
25
26.5
2.12
V
0.75
TA = +25 oC
1/V
28
µA
Typical Operating Characteristics
(VIN = VDIM = 48V, RSENSE = 0.3Ω, L = 220µH (connected between IN and CS). Typical values are at TA = +25°C, unless otherwise
noted.)
1 LED
80
15 LEDs
90
13 LEDs
80
11 LEDs
70
9 LEDs
7 LEDs
60
5 LEDs
50
3 LEDs
40
30
75
70
15
25
35
VIN (V)
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45
55
65
450
13 LEDs
11 LEDs
9 LEDs
350
300
7 LEDs
5 LEDs
250
200
3 LEDs
150
1 LED
15 LEDs
400
20
100
10
50
1 LED
16 LEDs
0
0
5
500
FREQUENCY (kHz)
90
85
100
MAX16832A toc02
11 LEDs 13 LEDs 15 LEDs
DUTY CYCLE (%)
EFFICIENCY (%)
95
9 LEDs
7 LEDs
5 LEDs
3 LEDs
MAX16832A toc01
100
FREQUENCY
vs. INPUT VOLTAGE
DUTY CYCLE
vs. INPUT VOLTAGE
MAX16832A toc03
EFFICIENCY
vs. INPUT VOLTAGE
5
15
25
35
VIN (V)
45
55
65
5
15
25
35
45
55
65
VIN (V)
Maxim Integrated | 3
2MHz, High-Brightness LED Drivers
with Integrated MOSFET and
High-Side Current Sense
MAX16832A/MAX16832C
Typical Operating Characteristics (continued)
(VIN = VDIM = 48V, RSENSE = 0.3Ω, L = 220µH (connected between IN and CS). Typical values are at TA = +25°C, unless otherwise
noted.)
1.02
1.01
13 LEDs
11 LEDs 15 LEDs
7 LEDs 9 LEDs
1 LED 3 LEDs 5 LEDs
1.00
0.99
MAX16832A toc05
1.03
450
QUIESCENT CURRENT (μA)
NORMALIZED ILED CURRENT
1.04
MAX16832A toc06
500
MAX16832A toc04
1.05
PWM DIMMING
AT 200Hz (10% DUTY CYCLE)
QUIESCENT CURRENT
vs. INPUT VOLTAGE
NORMALIZED ILED CURRENT
vs. INPUT VOLTAGE
0.98
400
VIN = 48V
8 LEDs
350
ILED
200mA/div
300
250
200
0
150
0.97
100
0.96
50
0.95
0
VDIM
5V/div
0
VDIM = 0V
0 5 10 15 20 25 30 35 40 45 50 55 60 65
0 5 10 15 20 25 30 35 40 45 50 55 60 65
VIN (V)
VIN (V)
PWM DIMMING
AT 200Hz (90% DUTY CYCLE )
1ms/div
PWM DIMMING
AT 20kHz (90% DUTY CYCLE)
MAX16822A toc07
MAX16832A toc08
ILED
200mA/div
ILED
200mA/div
0
0
VIN = 48V
8 LEDs
1ms/div
10μs/div
LED CURRENT
vs. VTEMP_I
ILED
vs. TEMPERATURE
0
MAX16832A toc10
1.0
MAX16832A toc09
800
750
700
650
600
550
500
450
400
350
300
250
200
150
100
50
0
0.9
0.8
0.7
ILED (A)
LED CURRENT (mA)
VIN = 48V
8 LEDs
VDIM
5V/div
VDIM
5V/div
0
0.6
0.5
0.4
0.3
0.2
0.1
VIN = 48V
0
0
0.4
0.8
1.2
1.6
VTEMP_I (V)
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2.0
2.4
2.8
-40 -25 -10 5 20 35 50 65 80 95 110 125
TEMPERATURE (°C)
Maxim Integrated | 4
2MHz, High-Brightness LED Drivers
with Integrated MOSFET and
High-Side Current Sense
MAX16832A/MAX16832C
Typical Operating Characteristics (continued)
(VIN = VDIM = 48V, RSENSE = 0.3Ω, L = 220µH (connected between IN and CS). Typical values are at TA = +25°C, unless otherwise
noted.)
ITEMP_I
vs. TEMPERATURE
LXRDSON
vs. TEMPERATURE
0.6
29.5
29.0
28.5
0.5
0.4
VIN = 6.5V
0.3
ITEMP_I (μA)
LXRDSON (Ω)
VIN = 48V
30.0
MAX16832A toc12
VIN = 65V
MAX16832A toc11
0.7
28.0
27.5
27.0
26.5
26.0
0.2
25.5
25.0
0.1
VIN = 48V
-40 -25 -10 5 20 35 50 65 80 95 110 125
-40 -25 -10 5 20 35 50 65 80 95 110 125
TEMPERATURE (°C)
TEMPERATURE (°C)
Pin Description
PIN
NAME
1
CS
Current-Sense Input. Connect a resistor between IN and CS to program the LED current.
2
IN
Positive Supply Voltage Input. Bypass with a 1µF or higher value capacitor to GND.
3
GND
4
PGND
5, 6
LX
7
DIM
8
TEMP_I
—
EP
FUNCTION
Ground
Power Ground
Switching Node
Logic-Level Dimming Input. Drive DIM low to turn off the current regulator. Drive DIM high to
enable the current regulator.
Thermal Foldback Control and Linear Dimming Input. Bypass with a 0.01µF capacitor to GND if
thermal foldback or analog dimming is used. See the Thermal Foldback section.
Exposed Pad. Connect EP to a large-area ground plane for effective power dissipation. Do not use
as the IC ground connection.
Detailed Description
The MAX16832A/MAX16832C are step-down, constantcurrent, HB LED drivers. These devices operate from a
+6.5V to +65V input voltage range. The maximum output
is 1A, if the part is used at temperatures up to TA =
+105°C, or 700mA, if it is used up to TA = +125°C. A
high-side current-sense resistor sets the output current
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and a dedicated PWM dimming input enables pulsed
LED dimming over a wide range of brightness levels.
A high-side current-sensing scheme and an on-board
current-setting circuitry minimize the number of external components while delivering LED current with ±3%
accuracy, using a 1% sense resistor. See Figure 1 for a
functional diagram.
Maxim Integrated | 5
2MHz, High-Brightness LED Drivers
with Integrated MOSFET and
High-Side Current Sense
MAX16832A/MAX16832C
IN
VCC
REGULATOR
MAX16832A
MAX16832C
VCC _ANA
ISET
OPEN LED
COMPARATOR
LX
VCC _ANA
CS
CURRENT-SENSE
COMPARATOR
0.45Ω, 65V
nMOS SWITCH
PWM
DIMMING
1.23V
BANDGAP
REF
GATE
DRIVER
UVLO
COMPARATOR
DIM
DIM
BUFFER
VCC _ANA
25μA
TEMP_I
PGND
VTFB_ON
2V
THERMAL
FOLDBACK
COMPARATOR
GND
Figure 1. Functional Diagram
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Maxim Integrated | 6
2MHz, High-Brightness LED Drivers
with Integrated MOSFET and
High-Side Current Sense
MAX16832A/MAX16832C
Undervoltage Lockout (UVLO)
The MAX16832A/MAX16832C include a UVLO with
500mV hysteresis. The internal MOSFET turns off when
VIN falls below 5.5V to 6.0V.
DIM Input
LED dimming is achieved by applying a PWM signal at
DIM. A logic level below 0.6V at DIM forces the
MAX16832A/MAX16832Cs’ output low, thus turning off
the LED current. To turn the LED current on, the logic
level at DIM must be greater than 2.8V.
Thermal Shutdown
The MAX16832A/MAX16832C thermal-shutdown feature
turns off the LX driver when the junction temperature
exceeds +165°C. The LX driver turns back on when the
junction temperature drops 10°C below the shutdown
temperature threshold.
Analog Dimming
The MAX16832A/MAX16832C offer an analog-dimming
feature that reduces the output current when the voltage at TEMP_I is below the internal 2V threshold voltage. The MAX16832A/MAX16832C achieve analog
dimming by either an external DC voltage source connected between TEMP_I and ground or by a voltage on
a resistor connected across TEMP_I and ground
induced by an internal current source of 25µA. When
the voltage at TEMP_I is below the internal 2V threshold
limit, the MAX16832A/MAX16832C reduce the LED current. Use the following formula to set the analog dimming current:
⎡
⎤
⎛ 1⎞
ITF (A) = ILED (A) × ⎢1− FBSLOPE ⎜ ⎟ × VTFB _ ON − VAD (V)⎥
⎝
⎠
V
⎣
⎦
(
)
where VTFB_ON = 2V and FBSLOPE = 0.75 are obtained
from the Electrical Characteristics table and VAD is the
voltage at TEMP_I.
Thermal Foldback
The MAX16832A/MAX16832C include a thermal-foldback feature that reduces the output current when the
temperature of the LED string exceeds a specified temperature point. These devices enter thermal-foldback
mode when the voltage drop on the NTC thermistor,
thermally attached to the LEDs and electrically connected between TEMP_I and ground, drops below the
internal 2V threshold limit.
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Applications Information
Selecting RSENSE to Set LED Current
The LED current is programmed with a current-sense
resistor connected between IN and CS. Use the following equation to calculate the value of this resistor:
RSENSE (Ω) =
1 (VSNSHI + VSNSLO )(V)
ILED (A)
2
where VSNSHI is the sense voltage threshold high and
VSNSLO is the sense voltage threshold low (see the
Electrical Characteristics table for values).
Current-Regulator Operation
The MAX16832A/MAX16832C regulate the LED current
using a comparator with hysteresis (see Figure 2). As
the current through the inductor ramps up and the voltage across the sense resistor reaches the upper
threshold, the internal MOSFET turns off. The internal
MOSFET turns on again when the inductor current
ramps down through the freewheeling diode until the
voltage across the sense resistor equals the lower
threshold. Use the following equation to determine the
operating frequency:
fSW =
(VIN − nVLED ) × nVLED × RSENSE
VIN × ΔV × L
where n is the number of LEDs, VLED is the forward
voltage drop of 1 LED, and ΔV = (VSNSHI - VSNSLO).
Inductor Selection
The MAX16832A/MAX16832C operate up to a switching frequency of 2MHz. For space-sensitive applications, the high switching frequency allows the size of
the inductor to be reduced. Use the following formula to
calculate an approximate inductor value and use the
closest standard value:
L(approx.) =
(VIN − nVLED ) × nVLED × RSENSE
VIN × ΔV × fSW
For component selection, use the MAX16832A/C Design
Tool available at: www.maximintegrated.com/MAX16832software.
Maxim Integrated | 7
2MHz, High-Brightness LED Drivers
with Integrated MOSFET and
High-Side Current Sense
MAX16832A/MAX16832C
HYSTERETIC
MODE
fSW
ILED
ΔI
AVG. LED
CURRENT
t
VDIM
t1
t2
t
Figure 2. Current-Regulator Operation
Freewheeling-Diode Selection
For stability and best efficiency, a low forward-voltage
drop diode with fast reverse-recovery time and low
capacitance is recommended. A Schottky diode is a
good choice as long as its breakdown voltage is high
enough to withstand the maximum operating voltage.
PCB Layout Guidelines
Careful PCB layout is critical to achieve low switching
losses and stable operation. In normal operation, there
are two power loops. One is formed when the internal
MOSFET is on and the high current flows from ground
through the input cap, R SENSE , the LED load, the
inductor, and the internal MOSFET back to ground. The
second loop is formed when the internal MOSFET is off
and the high current circulates from the input cap positive terminal through RSENSE, the LED load, the inductor, and the freewheeling diode and back to the input
cap positive terminal. Note that the current through
RSENSE, the LED load, and the inductor is basically DC
with some triangular ripple (low noise). The high-noise,
large signal, fast transition switching currents only flow
through the freewheeling diode to the input cap positive
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terminal, or through the MOSFET to ground and then to
the input cap positive terminal. Without a proper PCB
layout, these square-wave switching currents can create problems in a hysteretic LED driver.
The current control depends solely on the voltage
across RSENSE. Any noise pickup on this node induces
erratic switching of the internal MOSFET (the IC will
operate at a much higher frequency). To help prevent
this, place RSENSE as close as possible to CS and IN
and keep the sense traces short. It is especially important to keep the square-wave switching currents in the
freewheeling diode away from RSENSE. To minimize
interference, place the freewheeling diode on the opposite side of the IC as RSENSE and position the input
capacitor near the diode so it can return the high frequency currents to ground. The layout in Figure 3
should be used as a guideline. The dashed line shows
the path of the high frequency components that cause
disruption in operation. For a good thermal design, the
exposed pad on the IC should solder to a large pad
with many vias to the backside ground plane.
Maxim Integrated | 8
2MHz, High-Brightness LED Drivers
with Integrated MOSFET and
High-Side Current Sense
MAX16832A/MAX16832C
LED+
LED-
CFILTER
RSENSE
1
L
GND
LX
CIN
VIAS FOR THERMAL TRANSFER
TO BACKSIDE GROUND PLANE
VIN
D
tOFF AND tON CURRENT PATHS
KEEP THIS LOOP TIGHT.
Figure 3. PCB Layout
Ordering Information
Pin Configuration
PART
TOP VIEW
+
CS
1
8
TEMP_I
IN
2
7
DIM
GND
3
6
LX
5
LX
MAX16832A
MAX16832C
PGND 4
SO-EP
Chip Information
PROCESS: BiCMOS
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TEMP RANGE
PIN-PACKAGE
MAX16832AASA+
-40°C to +125°C
8 SO-EP*
MAX16832AASA/V+
-40°C to +125°C
8 SO-EP*
MAX16832CASA+
-40°C to +125°C
8 SO-EP*
+Denotes a lead(Pb)-free/RoHS-compliant package.
*EP = Exposed pad.
/V denotes an automotive qualified part.
Package Information
For the latest package outline information and land patterns (footprints), go to www.maximintegrated.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.
8 SO-EP
S8E-12
21-0111
90-0150
Maxim Integrated | 9
MAX16832A/MAX16832C
2MHz, High-Brightness LED Drivers
with Integrated MOSFET and
High-Side Current Sense
Revision History
REVISION
NUMBER
REVISION
DATE
PAGES
CHANGED
0
5/08
Initial release
—
1
9/08
Introduced the MAX16832C
1
2
5/09
Revised General Description, Features, Absolute Maximum Ratings, and
Detailed Description
3
2/10
Updated PCB Layout Guidelines and added Figure 3
4
8/10
Corrected Functional Diagram and added Soldering (reflow) to Absolute
Maximum Ratings
5
3/12
Updated Sense Voltage Threshold High and DIM Turn-On Time in Electrical
Characteristics
6
7/12
Added automotive qualified part to Ordering Information
1
7
2/15
Updated Applications and Benefits and Features sections
1
DESCRIPTION
1, 2, 5
8, 9
2, 5, 6
2, 3
For pricing, delivery, and ordering information, please contact Maxim Direct at 1-888-629-4642, or visit Maxim Integrated’s website at www.maximintegrated.com.
Maxim Integrated cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim Integrated product. No circuit patent
licenses are implied. Maxim Integrated reserves the right to change the circuitry and specifications without notice at any time. The parametric values (min and
max limits) shown in the Electrical Characteristics table are guaranteed. Other parametric values quoted in this data sheet are provided for guidance.
Maxim Integrated and the Maxim Integrated logo are trademarks of Maxim Integrated Products, Inc.
© 2015 Maxim Integrated Products, Inc. | 10
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