MAX5068EAUE ,10.8 to 24 V, high-frequency, current-mode PWM controller with accurate programmable oscillatorApplications Pin ConfigurationsUniversal-Input AC Power SuppliesTOP VIEWIsolated Telecom Power Supp ..
MAX5069CAUE+ ,High-Frequency, Current-Mode PWM Controller with Accurate Oscillator and Dual FET DriversELECTRICAL CHARACTERISTICS(V = +12V for the MAX5069C/D, V = +23.6V for the MAX5069A/B at startup, t ..
MAX5069CAUE+T ,High-Frequency, Current-Mode PWM Controller with Accurate Oscillator and Dual FET DriversApplicationsUniversal-Input AC Power SuppliesPin ConfigurationIsolated Telecom Power SuppliesNetwor ..
MAX506ACPP ,Quad 8-Bit DACs with Rail-to-Rail Voltage OutputsELECTRICAL CHARACTERISTICS
(VDD = +5V 110%, Vss = 0V to -5.5V, AGND = DGND = 0V, VREF = 4V, RL = ..
MAX506ACPP ,Quad 8-Bit DACs with Rail-to-Rail Voltage OutputsFeatures
. Opennefrom Single +5VS|pplyor Duaieivsupphse
. Output Buffer Amplifiers Swing Rail-to- ..
MAX506ACWP ,Quad 8-Bit DACs with Rail-to-Rail Voltage OutputsELECTRICAL CHARACTERISTICS
(VDD = +5V 110%, Vss = 0V to -5.5V, AGND = DGND = 0V, VREF = 4V, RL = ..
MAX932CUA+ ,Ultra-Low-Power, Low-Cost Comparators with 2% ReferenceMAX931-MAX93419-0194; Rev 1; 2/97Ultra Low -Pow er, Low -CostComparators w ith 2% Reference________ ..
MAX932ESA ,Ultra Low-Power, Low-Cost Comparators with 2eferenceELECTRICAL CHARACTERISTICS—5V Operation (continued)(V+ = 5V, V- = GND = 0V, T = T to T , unless oth ..
MAX932ESA+ ,Ultra-Low-Power, Low-Cost Comparators with 2% ReferenceGeneral Description ________
MAX932ESA+T ,Ultra-Low-Power, Low-Cost Comparators with 2% ReferenceApplications5 HYSTBattery-Powered SystemsThreshold Detectors6 REFMAX931Window ComparatorsV- GND2 1O ..
MAX933CPA ,Ultra Low-Power, Low-Cost Comparators with 2eferenceApplications5 HYSTBattery-Powered SystemsThreshold Detectors6 REFMAX931Window ComparatorsV- GND21Os ..
MAX933CSA ,Ultra Low-Power, Low-Cost Comparators with 2eferenceGeneral Description ________
MAX5068BAUE-MAX5068EAUE
10.8 to 24 V, high-frequency, current-mode PWM controller with accurate programmable oscillator
General DescriptionThe MAX5068 is a high-frequency, current-mode,
pulse-width modulation (PWM) controller that integrates
all the building blocks necessary for implementing AC-
DC or DC-DC fixed-frequency power supplies. Isolated
or nonisolated power supplies are easily constructed
using either primary- or secondary-side regulation.
Current-mode control with leading-edge blanking sim-
plifies control-loop design, and a programmable inter-
nal slope-compensation circuit stabilizes the current
loop when operating at duty cycles above 50%. The
MAX5068A/B limit the maximum duty cycle to 50% for
use in single-ended forward converters. The
MAX5068C/D/E/F allow duty cycles up to 75%. The
MAX5068 features an accurate externally programma-
ble oscillator that simplifies system design.
An input undervoltage lockout (UVLO) programs the
input-supply startup voltage and ensures proper opera-
tion during brownout conditions.
A single external resistor programs the output switching
frequency from 12.5kHz to 1.25MHz. The MAX5068A/
B/C/E provide a SYNC input for synchronization to an
external clock. The maximum FET-driver duty cycle is
50% for the MAX5068A/B and 75% for the MAX5068C/
D/E/F. Programmable hiccup current limit provides
additional protection under severe faults.
The MAX5068 is specified over the -40°C to +125°C
automotive temperature range and is available in a
16-pin thermally enhanced TSSOP-EP package. Refer to
the MAX5069 data sheet for dual FET-driver applications.
Warning:The MAX5068 is designed to work with high
voltages. Exercise caution.
ApplicationsUniversal-Input AC Power Supplies
Isolated Telecom Power Supplies
Networking System Power Supplies
Server Power Supplies
Industrial Power Conversion
FeaturesCurrent-Mode Control with 47µA (typ) Startup
CurrentResistor-Programmable ±4.5% Accurate
Switching Frequency:
25kHz to 1.25MHz (MAX5068A/B)
12.5kHz to 625kHz (MAX5068C/D/E/F)Rectified 85VACto 265VACor 36VDCto 72VDC
Input (MAX5068A/C/D)Input Directly Driven from 10.8V to 24V
(MAX5068B/E/F)Frequency Synchronization Input
(MAX5068A/B/C/E)Programmable Dead Time and Slope
CompensationProgrammable Startup Voltage (UVLO)Programmable UVLO Hysteresis
(MAX5068A/B/D/F)Integrating Fault Protection (Hiccup)-40°C to +125°C Automotive Temperature Range16-Pin Thermally Enhanced TSSOP-EP Package
MAX5068
High-Frequency, Current-Mode PWM Controller
with Accurate Programmable Oscillator
Pin Configurations
Ordering Information19-3176; Rev 1; 7/04
*EP = Exposed pad.
Selector Guide appears at end of data sheet.
MAX5068
High-Frequency, Current-Mode PWM Controller
with Accurate Programmable Oscillator
ABSOLUTE MAXIMUM RATINGS
ELECTRICAL CHARACTERISTICS
(VIN = +12V for the MAX5068B/E/F; VIN= +23.6V for the MAX5068A/C/D at startup, then reduces to +12V; CIN= CREG5= 0.1µF;
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.
IN to PGND ............................................................-0.3V to +30V
IN to AGND.............................................................-0.3V to +30V
VCCto PGND..........................................................-0.3V to +13V
VCCto AGND..........................................................-0.3V to +13V
FB, COMP, CS, HYST, SYNC, REG5 to AGND........-0.3V to +6V
UVLO/EN, RT, DT, SCOMP, FLTINT to AGND.........-0.3V to +6V
NDRV to PGND...........................................-0.3V to (VCC+ 0.3V)
AGND to PGND.....................................................-0.3V to +0.3V
Continuous Power Dissipation
16-Pin TSSOP-EP (derate 21.3mW/°C above +70°C)...1702mW
Operating Temperature Range..........................-40°C to +125°C
Maximum Junction Temperature.....................................+150°C
Storage Temperature Range.............................-60°C to +150°C
Lead Temperature (soldering, 10s).................................+300°C
MAX5068
High-Frequency, Current-Mode PWM Controller
with Accurate Programmable Oscillator
ELECTRICAL CHARACTERISTICS (continued)
(VIN = +12V for the MAX5068B/E/F; VIN= +23.6V for the MAX5068A/C/D at startup, then reduces to +12V; CIN= CREG5= 0.1µF;
MAX5068
High-Frequency, Current-Mode PWM Controller
with Accurate Programmable Oscillator
Note 1:The MAX5068 is 100% tested at TA= +25°C. All limits over temperature are guaranteed by design.
Note 2:The MAX5068A/B are intended for use in universal-input power supplies. The internal clamp circuit is used to prevent the
bootstrap capacitor (C1 in Figure1) from charging to a voltage beyond the absolute maximum rating of the device when
UVLO/EN is low. The maximum current to VIN(hence to clamp) when UVLO is low (device is in shutdown) must be external-
ly limited to 2mA. Clamp currents higher than 2mA may result in clamp voltages higher than 30V, thus exceeding the
absolute maximum rating for VIN. For the MAX5068C/D, do not exceed the 24V maximum operating voltage of the device.
Note 3:Reference voltage (VREF) is measured with FB connected to COMP (see the Functional Diagram).
Note 4:The SYNC frequency must be at least 25% higher than the programmed oscillator frequency.
Note 5:The internal oscillator clock cycle.
Note 6:The MAX5068A/B driver switching frequency is one-half of the oscillator frequency. The MAX5068C/D/E/F driver switching
frequency is one-quarter of the oscillator frequency.
ELECTRICAL CHARACTERISTICS (continued)
(VIN = +12V for the MAX5068B/E/F; VIN= +23.6V for the MAX5068A/C/D at startup, then reduces to +12V; CIN= CREG5= 0.1µF;
CVCC= 1µF; RRT= 100kΩ; NDRV = floating; TA= TMINto TMAX, unless otherwise noted. Typical values are at TA= +25°C.) (Note 1)
MAX5068
High-Frequency, Current-Mode PWM Controller
with Accurate Programmable Oscillator
BOOTSTRAP UVLO WAKE-UP LEVEL
vs. TEMPERATURE
MAX5068 toc01
TEMPERATURE (°C)
(V)603510-15
BOOTSTRAP UVLO SHUTDOWN LEVEL
vs. TEMPERATUREMAX5068 toc02
TEMPERATURE (°C)
(V)603510-15
UVLO/EN WAKE-UP THRESHOLD
vs. TEMPERATURE
MAX5068 toc03
TEMPERATURE (°C)
UVLO/EN (V)603510-15
UVLO/EN SHUTDOWN THRESHOLD
vs. TEMPERATURE
MAX5068 toc04
TEMPERATURE (°C)
UVLO/EN (V)603510-15
VIN SUPPLY CURRENT IN
UNDERVOLTAGE LOCKOUT vs. TEMPERATURE
MAX5068 toc05
TEMPERATURE (°C)
ISTART603510-15
VIN SUPPLY CURRENT AFTER STARTUP
vs. TEMPERATURE
MAX5068 toc06
TEMPERATURE (°C)
IIN
(mA)603510-15
VCC vs. TEMPERATURE
MAX5068 toc07
TEMPERATURE (°C)
(V)603510-15
REG5 OUTPUT VOLTAGE
vs. OUTPUT CURRENT
MAX5068 toc08
OUTPUT CURRENT (mA)
REG5 (V)
REG5 vs. TEMPERATURE
MAX5068 toc09
TEMPERATURE (°C)
REG5 (V)603510-15
Typical Operating Characteristics
(VIN = +12V for the MAX5068B/E/F; VIN= +23.6V for MAX5068A/C/D at startup, then reduces to +12V; CIN= CREG5= 0.1µF;
CVCC= 1µF; RRT= 100kΩ; NDRV = floating; VFB= 0; VCOMP= floating; VCS= 0; TA= +25°C, unless otherwise noted.)
MAX5068
High-Frequency, Current-Mode PWM Controller
with Accurate Programmable Oscillator
Typical Operating Characteristics (continued)(VIN = +12V for the MAX5068B/E/F; VIN= +23.6V for MAX5068A/C/D at startup, then reduces to +12V; CIN= CREG5= 0.1µF;
CVCC= 1µF; RRT= 100kΩ; NDRV = floating; VFB= 0; VCOMP= floating; VCS= 0; TA= +25°C, unless otherwise noted.)
MAX5068
High-Frequency, Current-Mode PWM Controller
with Accurate Programmable Oscillator
FLTINT CURRENT vs. TEMPERATUREMAX5068 toc19
TEMPERATURE (°C)
FLTINT CURRENT (603510-15
HYST RON vs. TEMPERATURE
MAX5068 toc20
TEMPERATURE (°C)603510-15
NDRV SWITCHING FREQUENCY (fSW)
vs. RRT
MAX5068 toc21
RRT (MΩ)
(MHz)
NDRV SWITCHING FREQUENCY
vs. TEMPERATURE
MAX5068 toc22
TEMPERATURE (°C)
NDRV SWITCHING FREQUENCY (kHz)
NDRV SWITCHING FREQUENCY
vs. TEMPERATURE
MAX5068 toc23
TEMPERATURE (°C)
NDRV SWITCHING FREQUENCY (kHz)
NDRV SWITCHING FREQUENCY
vs. TEMPERATURE
MAX5068 toc24
TEMPERATURE (°C)
NDRV SWITCHING FREQUENCY (kHz)
DEAD TIME vs. TEMPERATURE
MAX5068 toc25
TEMPERATURE (°C)
TIME (ns)
DEAD TIME vs. RDT
MAX5068 toc26
RDT (kΩ)
TIME (ns)
Typical Operating Characteristics (continued)
(VIN = +12V for the MAX5068B/E/F; VIN= +23.6V for MAX5068A/C/D at startup, then reduces to +12V; CIN= CREG5= 0.1µF;
CVCC= 1µF; RRT= 100kΩ; NDRV = floating; VFB= 0; VCOMP= floating; VCS= 0; TA= +25°C, unless otherwise noted.)
MAX5068
High-Frequency, Current-Mode PWM Controller
with Accurate Programmable Oscillator
Pin Description
Detailed DescriptionThe MAX5068 is a current-mode PWM controller for use
in isolated and nonisolated power-supply applications.
A bootstrap UVLO with a programmable hysteresis,
very low startup, and low operating current result in
high-efficiency universal-input power supplies. In addi-
tion to the internal bootstrap UVLO, the device also
offers programmable input startup and turn-off volt-
ages, programmed through the UVLO/EN input. When
using the MAX5068 in the bootstrapped mode, if the
power-supply output is shorted, the tertiary winding
voltage drops below the 10V threshold, causing the
bootstrap UVLO to turn off the gate drive to the external
power MOSFET, reinitiating a startup sequence with
soft-start.
The MAX5068 includes a cycle-by-cycle current limit
that turns off the gate drive to the external MOSFET
during an overcurrent condition. The MAX5068 integrat-
ing fault protection reduces average power dissipation
during persistent fault conditions (see the Integrating
Fault Protectionsection).
The MAX5068 features a very accurate, wide-range,
programmable oscillator that simplifies and optimizes
the design of the magnetics. The MAX5068A/C/D are
well suited for universal-input (rectified 85VACto
265VAC) or telecom (-36VDCto -72VDC) power sup-
plies. The MAX5068B/E/F are well suited for low-input
voltage (10.8VDCto 24VDC) power supplies.
The MAX5068 high-frequency, universal input, offline/
telecom, current-mode PWM controller integrates all the
building blocks necessary for implementing AC-DC and
DC-DC fixed-frequency power supplies. Isolated or non-
isolated power supplies are easily constructed using
either primary- or secondary-side regulation. Current-
mode control with leading-edge blanking simplifies con-
trol-loop design, and an external slope-compensation
control stabilizes the current loop when operating at
duty cycles above 50% (MAX5068C/D/E/F). The
MAX5068A/B limit the maximum duty cycle to 50% for
use in single-ended forward converters. The
MAX5068C/D/E/F allow duty cycles up to 75% for use in
flyback converters.
An input undervoltage lockout (UVLO) programs the
input-supply startup voltage and ensures proper opera-
tion during brownout conditions. An external voltage-
divider programs the supply startup voltage. The
MAX5068A/B/D/F feature a programmable UVLO hys-
teresis. The MAX5068A/C/D feature an additional internal
bootstrap UVLO with large hysteresis that requires a min-
imum startup voltage of 23.6V. The MAX5068B/E/F start
up from a minimum voltage of 10.8V. Internal digital soft-
start reduces output-voltage overshoot at startup.
A single external resistor programs the switching fre-
quency from 12.5kHz to 1.25MHz. The MAX5068A/B/C/E
provide a SYNC input for synchronization to an external
clock. The maximum FET driver duty cycle is 50% for the
MAX5068A/B, and 75% for the MAX5068C/D/E/F.
Integrating fault protection ignores transient overcurrent
conditions for a set length of time. The length of time is
programmed by an external capacitor. The internal ther-
mal-shutdown circuit protects the device if the junction
temperature should exceed +170°C.
Power supplies designed with the MAX5068 use a
high-value startup resistor, R1, which charges a reser-
voir capacitor, C1 (Figure1). During this initial period,
while the voltage is less than the internal bootstrap
UVLO threshold, the device typically consumes only
47µA of quiescent current. This low startup current and
the large bootstrap UVLO hysteresis help to minimize
the power dissipation across R1, even at the high end
of the universal AC input voltage (265VAC).
The MAX5068 includes a cycle-by-cycle current limit
that turns off the gate to the external MOSFET during an
overcurrent condition. When using the MAX5068A/C/D
in the bootstrap mode (if the power-supply output is
shorted), the tertiary winding voltage drops below the
9.74V bootstrap UVLO to turn off the gate to the exter-
nal power MOSFET. This reinitiates a startup sequence
with soft-start.
Current-Mode ControlThe MAX5068 offers a current-mode control operation
feature, such as leading-edge blanking with a dual
internal path that only blanks the sensed current signal
applied to the input of the PWM controller. The current-
limit comparator monitors CS at all times and provides
cycle-by-cycle current limit without being blanked. The
leading-edge blanking of the CS signal prevents the
PWM comparator from prematurely terminating the on
cycle. The CS signal contains a leading-edge spike
that results from the MOSFET gate charge current, and
the capacitive and diode reverse-recovery current of
the power circuit. Since this leading-edge spike is nor-
mally lower than the current-limit comparator threshold,
current limiting is provided under all conditions.
Use the MAX5068C/D/E/F in flyback applications where
wide line voltage and load-current variations are
expected. Use the MAX5068A/B for forward/flyback
converters where the maximum duty must be limited to
less than 50%.
MAX5068
High-Frequency, Current-Mode PWM Controller
with Accurate Programmable Oscillator
MAX5068Use the MAX5068C/D/E/F in forward converter applica-
tions with greater than 50% duty cycle. The large duty
cycle results in much lower operating primary RMS cur-
rent through the MOSFET switch and, in most cases,
requires a smaller output filter capacitor. The major dis-
advantage to this is that the MOSFET voltage rating
must be higher. The MAX5068C/D/E/F capacitor
adjustable-slope-compensation feature allows for easy
stabilization of the inner current loop.
Undervoltage LockoutThe MAX5068 features an input voltage UVLO/EN func-
tion to enable the PWM controller before any operation
can begin. The MAX5068C/E shut down if the voltage
at UVLO/EN falls below its 1.18V threshold. The
MAX5068A/B/D/F also incorporate an UVLO hysteresis
input to set the desired turn-off voltage.
MAX5068C/E UVLO AdjustmentThe MAX5068C/E have an input voltage UVLO/EN with
a 1.231V threshold. Before any operation can com-
mence, the UVLO/EN voltage must exceed the 1.231V
threshold. The UVLO circuit keeps the PWM compara-
tor, ILIM comparator, oscillator, and output driver shut
down to reduce current consumption (see the
Functional Diagram).
Calculate R6 in Figure2 by using the following formula:
where VULR2is the UVLO/EN’s 1.231V rising threshold
and VONis the desired startup voltage. Choose an R7
value in the 20kΩrange.
After a successful startup, the MAX5068C/E shut down if
the voltage at UVLO/EN drops below its 1.18V threshold.
High-Frequency, Current-Mode PWM Controller
with Accurate Programmable Oscillator
