MAX5021EUA ,Current-Mode PWM Controllers for Isolated Power SuppliesApplicationsMAX5021EUA 50% -40°C to +85°C 8 µ MAX —Universal Off-Line Power SuppliesMAX5021EPA 50% ..
MAX5021EUT+T ,Current-Mode PWM Controllers for Isolated Power SuppliesApplicationsMAX5021EUA 50% -40°C to +85°C 8 μMAX —Universal Off-Line Power SuppliesMAX5021EPA 50% ..
MAX5023LASA ,65V, low-quiescent-current, high-voltage linear regulator with mP reset and watchdog timerMAX5023/MAX502419-2619; Rev 0; 10/0265V, Low-Quiescent-Current, High-Voltage LinearRegulators with ..
MAX5023LASA+ ,65V, Low-Quiescent-Current, High-Voltage Linear Regulators with µP Reset and Watchdog TimerFeaturesThe MAX5023/MAX5024 high-voltage linear regulators ● Wide Operating Input Voltage Range +6. ..
MAX5023MASA ,65V, low-quiescent-current, high-voltage linear regulator with mP reset and watchdog timerFeaturesThe MAX5023/MAX5024 high-voltage linear regulators Wide Operating Input Voltage Rangeopera ..
MAX5023MASA+ ,65V, Low-Quiescent-Current, High-Voltage Linear Regulators with µP Reset and Watchdog TimerFeaturesThe MAX5023/MAX5024 high-voltage linear regulators ● Wide Operating Input Voltage Range +6. ..
MAX918EUK-T ,SOT23 / 1.8V / Nanopower / Beyond-the-Rails Comparators With/Without Referencefeatures make the MAX917–MAX920 family of(MAX917/MAX918)comparators ideal for all 2-cell battery
MAX919ESA ,SOT23 / 1.8V / Nanopower / Beyond-the-Rails Comparators With/Without Referenceapplications,including monitoring/management. ♦ Input Voltage Range Extends 200mV Beyond-the-RailsT ..
MAX919ESA+ ,SOT23, 1.8V, Nanopower, Beyond-the-Rails Comparators With/Without Referenceapplications,Beyond-the-Railsincluding monitoring/management. ♦ CMOS Push-Pull Output with ±8mA Dri ..
MAX919EUK+ ,SOT23, 1.8V, Nanopower, Beyond-the-Rails Comparators With/Without ReferenceELECTRICAL CHARACTERISTICS—MAX917/MAX918(V = +5V, V = 0V, V = V , T = -40°C to +85°C, unless otherw ..
MAX919EUK+T ,SOT23, 1.8V, Nanopower, Beyond-the-Rails Comparators With/Without Referencefeatures make the MAX917–MAX920 family of♦ Input Voltage Range Extends 200mV comparators ideal for ..
MAX919EUK-T ,SOT23 / 1.8V / Nanopower / Beyond-the-Rails Comparators With/Without ReferenceELECTRICAL CHARACTERISTICS—MAX917/MAX918(V = +5V, V = 0, V = V , T = -40°C to +85°C, unless otherwi ..
MAX5021EUA
Current-Mode PWM Controllers for Isolated Power Supplies
General DescriptionThe MAX5021/MAX5022 current-mode PWM controllers
contain all the control circuitry required for the design
of wide input voltage range isolated power supplies.
These devices are well suited for use in universal input
(85VAC to 265VAC) off-line or telecom (-36VDC to
-72VDC) power supplies.
An undervoltage lockout (UVLO) circuit with large hys-
teresis coupled with low startup and operating current
reduce power dissipation in the startup resistor and
allow use of ceramic bypass capacitors. The 262kHz
switching frequency is internally trimmed to ±12%
accuracy; this allows the optimization of the magnetic
and filter components resulting in compact, cost-effec-
tive power supplies. The MAX5021 with 50% maximum
duty cycle and MAX5022 with 75% maximum duty
cycle are recommended for forward converters and fly-
back converters, respectively. The MAX5021/MAX5022
are available in 6-pin SOT23, 8-pin µMAX, and 8-pin
DIP packages and are rated for operation over the
-40°C to +85°C temperature range.
ApplicationsUniversal Off-Line Power Supplies
Standby Power Supplies
Isolated Power Supplies
Isolated Telecom Power Supplies
Mobile Phone Chargers
FeaturesAvailable in a Tiny 6-Pin SOT23 Package50µA Typical Startup Current1.2mA Typical Operating CurrentLarge UVLO Hysteresis of 14VFixed Switching Frequency of 262kHz ±12%50% Maximum Duty Cycle Limit (MAX5021)75% Maximum Duty Cycle Limit (MAX5022)60ns Cycle-by-Cycle Current-Limit Response
Time
MAX5021/MAX5022
Current-Mode PWM Controllers for Isolated
Power Supplies
Pin Configuration
Ordering Information
Typical Operating Circuit
WARNING: The MAX5021/MAX5022 are designed to work
with high voltages. Exercise caution!
MAX5021/MAX5022
Current-Mode PWM Controllers for Isolated
Power Supplies
ABSOLUTE MAXIMUM RATINGS
ELECTRICAL CHARACTERISTICS(VIN= +11V to +28V, VCS= 0, OPTO is unconnected, 10nF bypass capacitors at VINand VCC, NDRV unconnected, TA= -40°C to
+85°C, unless otherwise noted. Typical values are at VIN= +12V, TA= +25°C, unless otherwise noted.) (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.
VINto GND.............................................................-0.3V to +30V
VCCto GND............................................................-0.3V to +13V
NDRV to GND.............................................-0.3V to (VCC+ 0.3V)
CS, OPTO to GND....................................................-0.3V to +6V
NDRV Short-Circuit to GND........................................Continuous
Continuous Power Dissipation (TA= +70°C)
6-Pin SOT23 (derate 8.7mW/°C above +70°C).............696mW
8-Pin µMAX (derate 4.5mW/°C above +70°C)..............362mW
8-Pin PDIP (derate 9.1mW/°C above +70°C)................727mW
Operating Temperature Range...........................-40°C to +85°C
Storage Temperature Range.............................-55°C to +150°C
Lead Temperature (soldering 10s)..................................+300°C
MAX5021/MAX5022
Current-Mode PWM Controllers for Isolated
Power Supplies
ELECTRICAL CHARACTERISTICS (continued)(VIN= +11V to +28V, VCS= 0, OPTO is unconnected, 10nF bypass capacitors at VINand VCC, NDRV unconnected, TA= -40°C to
+85°C, unless otherwise noted. Typical values are at VIN= +12V, TA= +25°C, unless otherwise noted.) (Note 1)
Note 1:All devices are 100% tested at TA= +25°C. All limits over temperature are guaranteed by characterization.
Note 2:This minimum current after startup is a safeguard that prevents the VINpin voltage from rising in the event
that OPTO and NDRV become unconnected.
Typical Operating Characteristics(VIN= 15V, TA = +25°C, unless otherwise noted.)
MAX5021/MAX5022
Current-Mode PWM Controllers for Isolated
Power Supplies
Typical Operating Characteristics (continued) (VIN= 15V, TA = +25°C, unless otherwise noted.)
Detailed DescriptionThe MAX5021/MAX5022 are current-mode PWM con-
trollers that have been specifically designed for use in
isolated power supplies. An undervoltage lockout cir-
cuit (UVLO) with a large hysteresis (14V) along with
very low startup and operating current result in high-
efficiency, universal input power supplies. Both devices
can be used in power supplies capable of operating
from a universal 85VAC to 265VAC line or the telecom
voltage range of -36VDC to -72VDC.
Power supplies designed with these devices use a
high-value startup resistor, RS, (series combination ofand R2) that charges a reservoir capacitor, C2 (see
Figure 1). During this initial period while the voltage is
less than the UVLO start threshold, the IC typically con-
sumes only 50µA of quiescent current. This low startup
current and the large UVLO hysteresis combined with
the use of a ceramic capacitor C2 keeps the power dis-
sipation in RSto less than 1/4W even at the high end of
the universal AC input voltage (265VAC).
The MAX5021/MAX5022 include a cycle-by-cycle cur-
rent limit which turns off the gate drive to the external
MOSFET during an overcurrent condition. If the output
on the secondary side of transformer T1 is shorted, the
tertiary winding voltage will drop below the 10V thresh-
old causing the UVLO circuit to turn off the gate drive to
the external power MOSFET, thus re-initiating the start-
up sequence.
StartupFigure 2 shows the voltages on VINand VCCduring
startup. Initially, both VINand VCCare 0V. After the line
voltage is applied, C2 charges through the startup
resistor, RS, to an intermediate voltage at which point
the internal reference and regulator begin charging C3
(see Figure 1). The bias current consumed by the
device during this period is only 50µA; the remaining
input current charges C2 and C3. Charging of C3 stops
when the VCCvoltage reaches approximately 9.5V,
while the voltage across C2 continues rising until it
reaches the wakeup level of 24V. Once VINexceeds
the UVLO threshold, NDRV begins switching the
MOSFET, transferring energy to the secondary and ter-
tiary outputs. If the voltage on the tertiary output builds
to higher than 10V (UVLO lower threshold), then startup
has been accomplished and sustained operation
will commence.
If VINdrops below 10V before startup is complete, then
the IC goes back into UVLO. In this case, increase the
value of C2 and/or use a MOSFET with a lower gate-
charge requirement.
Startup Time ConsiderationsThe VINbypass capacitor C2 supplies current immediate-
ly after wakeup. The size of C2 will determine the number
of cycles available for startup. Large values for C2 will
increase the startup time, but will also supply more gate
charge, allowing for more cycles after wakeup. If the
value of C2 is too small, VINwill drop below 10V because
MAX5021/MAX5022
Current-Mode PWM Controllers for Isolated
Power Supplies
MAX5021/MAX5022NDRV did not switch enough times to build up sufficient
voltage across the tertiary output to power the device.
The device will go back into UVLO and will not start. Use
a low-leakage ceramic or film capacitor for C2 and C3.
As a rule of thumb, off-line power supplies keep typical
startup times to less than 500ms even in low-line condi-
tions (85VAC input). Size the startup resistor, RS, to sup-
ply the maximum startup bias of the IC (85µA) plus the
additional current required for charging the capacitors
C2 and C3 in less than 500ms. This resistor dissipates
continuous power in normal operation, despite the fact
that it is only used during the startup sequence.
Therefore it must be chosen to provide enough current
for the low-line condition as well as have an appropriate
power rating for the high-line condition (265VAC). In
most cases, split the value into two resistors connected
in series for the required voltage of approximately
400VDC.
The typical value for C2 and C3 is 220nF. The startup
resistor, RS, provides both the maximum quiescent cur-
rent of 85µA and the charging current for C2 and C3.
Bypass capacitor C3 charges to 9.5V and C2 charges
to 24V all within the desired time period of 500ms, for
an overall average charging current of 15µA. Hence,
the startup resistor must provide a total of at least
100µA. Developing 100µA from an input voltage of
Current-Mode PWM Controllers for Isolated
Power SuppliesFigure 1. Universal 5W Off-Line Standby Power Supply
