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MAX5069CAUE+N/AN/a2500avaiHigh-Frequency, Current-Mode PWM Controller with Accurate Oscillator and Dual FET Drivers
MAX5069CAUE+TN/AN/a2500avaiHigh-Frequency, Current-Mode PWM Controller with Accurate Oscillator and Dual FET Drivers


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 ..
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MAX933CSA ,Ultra Low-Power, Low-Cost Comparators with 2eferenceGeneral Description ________


MAX5069CAUE+-MAX5069CAUE+T
High-Frequency, Current-Mode PWM Controller with Accurate Oscillator and Dual FET Drivers
neral DescriptionThe MAX5069 is a high-frequency, current-mode,
pulse-width modulation (PWM) controller (with dual
MOSFET drivers) that integrates all the building blocks
necessary for implementing AC-DC or DC-DC fixed-fre-
quency power supplies. Isolated or nonisolated push-
pull and half/full-bridge power supplies are easily
constructed using either primary- or secondary-side
regulation. Current-mode control with leading-edge
blanking simplifies control-loop design and a program-
mable internal slope-compensation circuit stabilizes the
current loop when operating at duty cycles above 50%.
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 oscillator frequen-
cy from 50kHz to 2.5MHz. The MAX5069A/D provide a
SYNC input for synchronization to an external clock. The
maximum FET-driver duty cycle for the MAX5069 is 50%.
Programmable dead time allows additional flexibility in
optimizing magnetic design and overcoming parasitic
effects. Programmable hiccup current limit provides
additional protection under severe faults.
The MAX5069 is specified over the -40°C to +125°C auto-
motive temperature range and is available in a
16-pin thermally enhanced TSSOP-EP package. Refer to
the MAX5068 data sheet for single FET-driver applications.
Warning:
The MAX5069 is designed to work with high
voltages. Exercise caution.
Applications

Universal-Input AC Power Supplies
Isolated Telecom Power Supplies
Networking System Power Supplies
Server Power Supplies
Industrial Power Conversion
Features
Current-Mode Control with 47μA (typ) Startup
Current
Oscillator Frequency Programmable to 2.5MHzResistor-Programmable ±4.5% Accurate
Switching Frequency
Dual Gate-Drive Output for Half/Full-Bridge or
Push-Pull Applications
Rectified 85VAC to 265VAC, or 36VDC to 72VDC
Input (MAX5069A/B)
Input Directly Driven from 10.8V to 24V
(MAX5069C/D)
Programmable Dead Time and Slope
Compensation
Programmable Startup Voltage (UVLO)Programmable UVLO Hysteresis (MAX5069B/C)Frequency Synchronization Input (MAX5069A/D)-40°C to +125°C Automotive Temperature Range16-Pin Thermally Enhanced TSSOP-EP Packageigh-Frequency, Current-Mode PWM Controlleith Accurate Oscillator and Dual FET DriversREG5
VCC
NDRVA
NDRVB
PGND
AGND
TOP VIEW
MAX5069
TSSOP-EP

SYNC(HYST*)
SCOMP
UVLO/EN
COMP
FLTINT
*MAX5069B/C.
Pin Configuration
Ordering Information

19-3175; Rev 1; 7/04
*EP = Exposed pad.
PARTTEMP RANGEPIN-PACKAGE

MAX5069AAUE-40°C to +125°C16 TSSOP-EP*
MAX5069BAUE-40°C to +125°C16 TSSOP-EP*
MAX5069CAUE-40°C to +125°C16 TSSOP-EP*
MAX5069DAUE-40°C to +125°C16 TSSOP-EP*
Selector Guide appears at end of data sheet.
igh-Frequency, Current-Mode PWM Controllerith Accurate Oscillator and Dual FET DriversABSOLUTE MAXIMUM RATINGS
ELECTRICAL CHARACTERISTICS

(VIN = +12V for the MAX5069C/D, VIN= +23.6V for the MAX5069A/B 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)
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
NDRVA, NDRVB to PGND..........................-0.3V to (VCC+ 0.3V)
AGND to PGND.....................................................-0.3V to +0.3V
Continuous Power Dissipation (TA= +70°C)
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
PARAMETERSYMBOLCONDITIONSMINTYPMAXUNITS
UNDERVOLTAGE LOCKOUT/STARTUP

Bootstrap UVLO Wake-Up LevelVSUVRVIN rising, MAX5069A/B19.6821.623.60V
Bootstrap UVLO Shutdown LevelVSUVFVIN falling, MAX5069A/B9.059.7410.43V
UVLO/EN Wake-Up ThresholdVULR2UVLO/EN rising1.2051.2301.255V
UVLO/EN Shutdown ThresholdVULF2UVLO/EN falling1.18V
HYST FET On-ResistanceRD S ( ON ) _H MAX5069B/C only, sinking 50mA,
VUVLO/EN = 0V10Ω
HYST FET Leakage CurrentILEAK_HVUVLO/EN = 2V, VHYST = 5V3nA
IN Supply Current In
Undervoltage LockoutISTARTVIN = +19V, VUVLO/EN < VULF24790μA
IN RangeVIN10.824.0V
INTERNAL SUPPLIES (VCC and REG5)

VCC Regulator Set PointVCCSPV IN = + 10.8V to + 24V , V C C sour ci ng 1μA to 25m A7.010.5V
REG5 Output VoltageVREG5IREG5 = 0 to 1mA4.855.005.15V
REG5 Short-Circuit Current LimitIREG5_SC18mA
fSW = 1.25MHz7IN Supply Current After StartupIINVIN = +24VfSW = 100kHz3mA
Shutdown Supply CurrentIVIN_SD90μA
GATE DRIVER (NDRVA, NDRVB)

ZOUT(LOW)NDRVA/NDRVB sinking 100mA24Driver Output ImpedanceZOUT(HIGH)NDRVA/NDRVB sourcing 25mA36Ω
Sinking1000Driver Peak Output CurrentINDRVSourcing650mA
PWM COMPARATOR

Comparator Offset VoltageVOS_PWMVCOMP > VCS1.301.602.00V
Comparator Propagation DelaytPD_PWMVCS = 0.1V40ns
Minimum On-TimetON(MIN)Includes tCS_BLANK110ns
CURRENT-LIMIT COMPARATOR

Current-Limit Trip ThresholdVCS298314330mV
igh-Frequency, Current-Mode PWM Controlleith Accurate Oscillator and Dual FET DriversPARAMETERSYMBOLCONDITIONSMINTYPMAXUNITS
CS Input Bias CurrentIB_CLVCS = 0V0+2μA
CS Blanking TimetCS_BLANK70ns
Propagation Delay from
Comparator Input to NDRV_tPD_CL50mV overdrive40ns
IN CLAMP VOLTAGE

IN Clamp VoltageVIN_CLAMPIN sinking 2mA (Note 2)24.026.029.0V
ERROR AMPLIFIER (FB, COMP)

Voltage GainAVRCOMP = 100kΩ to AGND80dB
Unity-Gain BandwidthBWRCOMP = 100kΩ to AGND,
CLOAD = 100pF to AGND5MHz
Phase MarginPMRCOMP = 100kΩ to AGND,
CLOAD = 100pF to AGND65D eg r ees
FB Input Offset VoltageVOS_FB3mV
High2.63.8COMP Clamp VoltageVCOMPLow0.41.1V
Error-Amplifier Output CurrentICOMPSinking or sourcing0.5mA
+25°C ≤ TA ≤ +125°C (Note 3)1.2151.2301.245Reference VoltageVREF
-40°C ≤ TA ≤ +125°C (Note 3)1.2051.2301.242
Input Bias CurrentIB_EA100300nA
COMP Short-Circuit CurrentICOMP_SC12mA
THERMAL SHUTDOWN

Thermal-Shutdown TemperatureTSD+170°C
Thermal HysteresisTHYST25°C
OSCILLATOR SYNC INPUT (MAX5069A/D only)

SYNC High-Level VoltageVIH_SYNC2.4V
SYNC Low-Level VoltageVIL_SYNC0.4V
SYNC Input Bias CurrentIB_SYNC10nA
Maximum SYNC FrequencyfSYNCfOSC = 2.5MHz (Note 4)3.125MHz
SYNC High-Level Pulse WidthtSYNC_HI30ns
SYNC Low-Level Pulse WidthtSYNC_LO30ns
DIGITAL SOFT-START

Soft-Start DurationtSS(Note 5)2047Cycles
Reference-Voltage StepVSTEP9.7mV
Reference-Voltage Steps During
Soft-Start127Steps
OSCILLATOR

Oscillator Frequency RangefOSCfOSC = (1011 / RRT)502500kHz
ELECTRICAL CHARACTERISTICS (continued)

(VIN = +12V for the MAX5069C/D, VIN= +23.6V for the MAX5069A/B 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)
igh-Frequency, Current-Mode PWM Controllerith Accurate Oscillator and Dual FET DriversNote 1:The MAX5069 is 100% tested at TA= +25°C. All limits over temperature are guaranteed by design.
Note 2:
The MAX5069A/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 MAX5069C/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.
PARAMETERSYMBOLCONDITIONSMINTYPMAXUNITS

NDRV_ Switching FrequencyfSWfSW = 1011 / (2 x RRT)251250kHz
RT VoltageVRT40kΩ < RRT < 500kΩ2.0V
fOSC ≤ 500kHz-2.5+2.5TA = +25°CfOSC > 500kHz-4+4
fOSC ≤ 500kHz-4.5+4.5Oscillator Accuracy
TA = -40°C to +125°CfOSC > 500kHz-6+6
Maximum Duty CycleDMAXDT connected to REG5100%
DEAD-TIME CONTROL (DT)

Dead TimetDTRDT = 24.9kΩ60ns
Dead-Time Disable VoltageVDT_DISABLEVREG5 -
0.5VV
Dead-Time Regulation VoltageVDT1.23V
INTEGRATING FAULT PROTECTION (FLTINT)

FLTINT Source CurrentIFLTINTVFLTINT = 0V60μA
FLTINT Shutdown ThresholdVFLTINT_SDVFLTINT rising2.8V
FLTINT Restart ThresholdVFLTINT_RSVFLTINT falling1.6V
SLOPE COMPENSATION

Slope CompensationVSLOPECSLOPE = 100pf, RT = 110kΩ15mV/μs
Slope-Compensation RangeVSLOPER090mV/μs
Slope-Compensation Voltage
RangeVSCOMP02.7V
ELECTRICAL CHARACTERISTICS (continued)

(VIN = +12V for the MAX5069C/D, VIN= +23.6V for the MAX5069A/B 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)
igh-Frequency, Current-Mode PWM Controlleith Accurate Oscillator and Dual FET DriversBOOTSTRAP UVLO WAKE-UP LEVEL
vs. TEMPERATURE
AX5069 toc01
TEMPERATURE (°C)
(V
MAX5069A/B
BOOTSTRAP UVLO SHUTDOWN LEVEL
vs. TEMPERATURE
AX5069 toc02
TEMPERATURE (°C)
(V
MAX5069A/B
UVLO/EN WAKE-UP THRESHOLD
vs. TEMPERATURE
AX5069 toc03
TEMPERATURE (°C)
(V
UVLO/EN RISING
UVLO/EN SHUTDOWN THRESHOLD
vs. TEMPERATURE
AX5069 toc04
TEMPERATURE (°C)
UVLO/EN FALLING
VIN SUPPLY CURRENT IN UNDERVOLTAGE
LOCKOUT vs. TEMPERATURE
AX5069 toc05
TEMPERATURE (°C)
T (μ
VIN = 19V
WHEN IN BOOTSTRAP UVLO (MAX5069A/B)
UVLO/EN (MAX5069C/D) IS LOW
VIN SUPPLY CURRENT AFTER STARTUP
vs. TEMPERATURE

AX5069 toc06
TEMPERATURE (°C)
IIN
(m603510-15
VIN = 24VfSW = 1.25MHz
fSW = 50kHz
fSW = 500kHz
fSW = 100kHz
fSW = 250kHz
VCC vs. TEMPERATURE

X5069 toc07
TEMPERATURE (°C)
(V603510-15
VIN = 19V, IIN = 25mA
VIN = 19V, IIN = 10mA
VIN = 10.8V, IIN = 10mA
VIN = 10.8V, IIN = 25mA
REG5 OUTPUT VOLTAGE
vs. OUTPUT CURRENT

AX5069 toc08
OUTPUT CURRENT (mA)
(V
RRT = 100kΩ
REG5 vs. TEMPERATURE
AX5069 toc09
TEMPERATURE (°C)
(V
VIN = 10.8V
100μA LOAD
1mA LOAD
Typical Operating Characteristics

(VIN= +23.6V for MAX5069A/B at startup, then reduces to +12V, VIN = +12V for the MAX5069C/D, CIN= CREG5= 0.1μF, CVCC= 1μF,
RRT= 100kΩ, NDRV_ = floating, VFB= 0V, VCOMP= floating, VCS= 0V, TA= +25°C, unless otherwise noted.)
igh-Frequency, Current-Mode PWM Controllerith Accurate Oscillator and Dual FET DriversTypical Operating Characteristics (continued)
(VIN= +23.6V for MAX5069A/B at startup, then reduces to +12V, VIN = +12V for the MAX5069C/D, CIN= CREG5= 0.1μF, CVCC= 1μF,
RRT= 100kΩ, NDRV_ = floating, VFB= 0V, VCOMP= floating, VCS= 0V, TA= +25°C, unless otherwise noted.)
REG5 OUTPUT VOLTAGE vs. VIN

AX5069 toc10
VIN (V)
(V20161814121024
IREG5 = 100μA
CS TRIP THRESHOLD
vs. TEMPERATURE

X5069 toc11
TEMPERATURE (°C)
(m
SWITCHING FREQUENCY
vs. TEMPERATURE
AX5069 toc12
TEMPERATURE (°C)
(kH
fSW = 500kHzTOTAL NUMBER OF
DEVICES = 200
MEAN
-3σ
+3σ
PROPAGATION DELAY FROM CS COMPARATOR
INPUT TO NDRV vs. TEMPERATURE

AX5069 toc13
TEMPERATURE (°C)
(n
INPUT CURRENT
vs. INPUT CLAMP VOLTAGE
AX5069 toc14
INPUT CLAMP VOLTAGE (V)
(m
INPUT CLAMP VOLTAGE
vs. TEMPERATURE
AX5069 toc15
TEMPERATURE (°C)
(V
ISINK = 2mA
NDRVA/NDRVB OUTPUT IMPEDANCE
vs. TEMPERATURE
AX5069 toc16
TEMPERATURE (°C)
(Ω
VIN = 24V
SINKING 100mA
NDRVA/NDRVB OUTPUT IMPEDANCE
vs. TEMPERATURE
AX5069 toc17
TEMPERATURE (°C)
(Ω
VIN = 24V
SOURCING 25mA
ERROR AMPLIFIER OPEN-LOOP GAIN
AND PHASE vs. FREQUENCY

MAX5069 toc18
FREQUENCY (Hz)
(d
(D
10M10100k1k
GAIN
PHASE
igh-Frequency, Current-Mode PWM Controlleith Accurate Oscillator and Dual FET DriversFLTINT CURRENT vs. TEMPERATURE
X5069 toc19
TEMPERATURE (°C)

HYST RON vs. TEMPERATURE
X5069 toc20
TEMPERATURE (°C)
(Ω
VIN = 24V
SINKING 50mA
NDRVA SWITCHING FREQUENCY (fSW)
vs. RRT
X5069 toc21
RRT (MΩ)
(M
NDRV SWITCHING FREQUENCY
vs. TEMPERATURE

AX5069 toc22
TEMPERATURE (°C)
(kH
fSW = 50kHz
NDRV SWITCHING FREQUENCY
vs. TEMPERATURE

5069 toc23
TEMPERATURE (°C)
(k
fSW = 500kHzfSW = 500kHz
DEAD TIME vs. TEMPERATURE

X5069 toc25
TEMPERATURE (°C)
(n
VIN = 24V
RDT = 24.9kΩ
RRT = 100kΩ
NDRV SWITCHING FREQUENCY
vs. TEMPERATURE

AX5069 toc24
TEMPERATURE (°C)
(kH
fSW = 1.25MHz
DEAD TIME vs. RDT

AX5069 toc26
RDT (kΩ)
(n
Typical Operating Characteristics (continued)
(VIN= +23.6V for MAX5069A/B at startup, then reduces to +12V, VIN = +12V for the MAX5069C/D, CIN= CREG5= 0.1μF, CVCC= 1μF,
RRT= 100kΩ, NDRV_ = floating, VFB= 0V, VCOMP= floating, VCS= 0V, TA= +25°C, unless otherwise noted.)
igh-Frequency, Current-Mode PWM Controllerith Accurate Oscillator and Dual FET DriversPin Description
PIN
MAX5069A
MAX5069D
MAX5069B
MAX5069C
NAMEFUNCTION
1RTOscillator-Timing Resistor. Connect a resistor from RT to AGND to set the internal oscillator
frequency.—SYNCExternal-Clock Sync Input. Connect SYNC to AGND when not using an external clock.2HYSTHysteresis Input3SCOMPSlope-Compensation Capacitor Connection4DTDead-Time Resistor Connection. Connect a resistor from DT to AGND to program the
output dead time. Connect to REG5 for NDRVA and NDRVB maximum 50% duty cycle.5UVLO/ENExternally Programmable Undervoltage Lockout. UVLO/EN programs the input start
voltage. Connect UVLO/EN to AGND to disable the output.6FBError-Amplifier Inverting Input7COMPError-Amplifier Output8FLTINT
Fault-Integration Input. A capacitor connected to FLTINT charges with an internal 60μA
current source during persistent current-limit faults. Switching terminates when VFLTINT is
2.8V. An external resistor connected in parallel discharges the capacitor. Switching
resumes when VFLTINT drops to 1.6V.9CSCurrent-Sense Resistor Connection10AGNDAnalog Ground. Connect to PGND.11PGNDPower Ground. Connect to AGND through a ground plane. 12NDRVBG ate- D r i ver O utp ut B. C onnect N D RV B to the g ate of the exter nal N - channel FE T.13NDRVAGate-Driver Output A. Connect NDRVA to the gate of the external N-channel FET.14VCC9V Linear-Regulator Output. Decouple VCC with a minimum 1μF ceramic capacitor to
AGND; also internally connected to the FET drivers.15INPower-Supply Input. IN provides power for all internal circuitry except the gate driver.
Decouple IN with 0.1μF to AGND (see the Typical Operating Circuit).16REG55V Linear-Regulator Output. Decouple REG5 to AGND with 0.1μF ceramic capacitor.EPPADExposed Paddle. Connect to GND.
tailed DescriptionThe MAX5069 is a current-mode, dual MOSFET driver,
PWM controller designed for isolated and nonisolated
push-pull or half-/full-bridge 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 pin.
The MAX5069 includes a cycle-by-cycle current limit
that turns off the gate drive to the external MOSFET
during an overcurrent condition. The MAX5069 integrat-
ing fault protection reduces average power dissipation
during persistent fault conditions (see the Integrating
Fault Protectionsection).
The MAX5069 features a very accurate, wide-range,
programmable oscillator that simplifies and optimizes
the design of the magnetics. The MAX5069A/B are well
suited for universal-input (rectified 85VAC to 265VAC)
or telecom (-36VDC to -72VDC) power supplies. The
MAX5069C/D are well suited for low-input voltage
(10.8VDC to 24VDC) power supplies.
The MAX5069 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. Push-
pull and half-/full-bridge isolated or nonisolated power
supplies are easily constructed using either primary- or
secondary-side regulation. Current-mode control with
leading-edge blanking simplifies control-loop design
and the programmable slope compensation stabilizes
the current loop when operating both FET drivers at a
combined 100% duty cycle.
An input UVLO programs the input-supply startup volt-
age and ensures proper operation during brownout con-
ditions. An external voltage-divider programs the supply
startup voltage. The MAX5069B/C feature a programma-
ble UVLO hysteresis. The MAX5069A/B feature an addi-
tional internal bootstrap UVLO with large hysteresis that
requires a minimum startup voltage of 23.6V. The
MAX5069A/D start up from a minimum voltage of 10.8V.
Internal digital soft-start reduces output-voltage over-
shoot at startup.single external resistor programs the switching fre-
quency of each MOSFET driver from 25kHz to
1.25MHz. The MAX5069A/D provide a SYNC input for
synchronization to an external clock. The maximum FET
driver duty cycle for each driver is limited to 50%.
Programmable dead time allows additional flexibility in
optimizing magnetic design and overcoming parasitic
effects. 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 thermal-shutdown circuit protects the
device should the junction temperature exceed
+170°C.
Power supplies designed with the MAX5069A/B 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 MAX5069 includes a cycle-by-cycle current limit
that turns off the gates to both external MOSFETs dur-
ing an overcurrent condition. When using the
MAX5069A/B in the bootstrap mode (if the power-sup-
ply output is shorted), the tertiary winding voltage
drops below the 9.74V threshold, causing the UVLO to
turn off the gate to the external power MOSFETs. This
reinitiates a startup sequence with soft-start.
Current-Mode Control

The MAX5069 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’s gate charge current,
and the capacitive and diode reverse-recovery current
of the power circuit. Since this leading-edge spike is
normally lower than the current-limit comparator thresh-
old, current limiting is provided under all conditions.
Use the MAX5069 in push-pull and half-/full-bridge appli-
cations where a large duty cycle is desired. The large
duty cycle results in much lower operating primary RMS
currents through the MOSFET switches, and in most
cases it results in a smaller inductor and output filter
capacitor. The MAX5069 adjusted slope compensation
allows for easy stabilization of the inner current loop.igh-Frequency, Current-Mode PWM Controlleith Accurate Oscillator and Dual FET Drivers
Undervoltage Lockout
The MAX5069 features an input voltage UVLO/EN func-
tion to enable the PWM controller before any operation
can begin. The MAX5069A/D shut down if the voltage
at UVLO/EN falls below its 1.18V threshold. The
MAX5069B/C also incorporate a UVLO hysteresis input
to set the desired turn-off voltage.
MAX5069A/D UVLO Adjustment

The MAX5069A/D 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 drivers 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 MAX5069A/D shut down
if the voltage at UVLO/EN drops below its 1.18V fall-
ing threshold.
MAX5069B/C UVLO with
Programmable Hysteresis

In addition to programmable undervoltage lockout dur-
ing startup, the MAX5069B/C incorporate a UVLO/ENVRON
ULR17 =⎛⎜⎞⎟×−igh-Frequency, Current-Mode PWM Controllerith Accurate Oscillator and Dual FET Drivers
MAX5069B
NDRVA
NDRVB
HYST
UVLO/EN
COMP
VCC
AGNDPGND
REG5
FLTINTC1
VIN
VOUT
SCOMPD3
R10
RHYST
Figure1. Nonisolated Power Supply with Programmable Input Supply Voltage
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