MAX5094AAUA+ Maxim Integrated Products, MAX5094AAUA+ Datasheet - Page 15

• Manufacturer Part Number: MAX5094AAUA+
• Description: IC PWM CONTROL HP 8-UMAX
• Manufacturer: Maxim Integrated Products

Specifications of MAX5094AAUA+

• Pwm Type: Current Mode
• Number Of Outputs: 1
• Frequency - Max: 1MHz
• Duty Cycle: 97%
• Voltage - Supply: 8 V ~ 25 V
• Buck: No
• Boost: No
• Flyback: Yes
• Inverting: No
• Doubler: No
• Divider: Yes
• Cuk: No
• Isolated: Yes
• Operating Temperature: -40°C ~ 125°C
• Package / Case: 8-MSOP, Micro8™, 8-uMAX, 8-uSOP,
• Frequency-max: 1MHz
• Duty Cycle (max): 97.5 %
• Output Voltage: 5 V
• Output Current: 1000 mA (Max)
• Mounting Style: SMD/SMT
• Switching Frequency: 1000 KHz
• Operating Supply Voltage: 8.4 V to 26.5 V
• Supply Current: 3 mA
• Maximum Operating Temperature: + 125 C
• Fall Time: 22 ns
• Minimum Operating Temperature: - 40 C
• Rise Time: 15 ns
• Synchronous Pin: No
• Topology: Flyback or Forward or Push-Pull
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

The MAX5095A/MAX5095B/MAX5095C use either an
external error amplifier when designed into a nonisolat-
ed converter or an error amplifier and optocoupler
when designed into an isolated power supply. The
COMP input is level-shifted and connected to the
inverting terminal of the PWM comparator (CPWM).
Connect the COMP input to the output of the external
error amplifier for nonisolated design. Pull COMP high
externally to 5V (or REF) and connect the optocoupler
transistor as shown in Figures 7 and 8. COMP can be
used for soft-start and also as a shutdown. See the
Typical Operating Characteristics to find the turn-off
COMP voltage at different temperatures.
The oscillator frequency is programmed by adding an
external capacitor and resistor at R
in the Typical Application Circuits). R
from R
nected from R
until its voltage reaches 2.8V. C
through an 8.3mA internal current sink until C
reaches 1.1V, at which time C
through R
sum of the charge and discharge times of C
the charge time as
The discharge time is then
The oscillator frequency will then be
For the MAX5094A/MAX5094C/MAX5095A, the convert-
er output switching frequency (f
oscillator frequency (f
MAX5094D/MAX5095B/MAX5095C, the output switch-
ing frequency is 1/2 the oscillator frequency.
High-Performance, Single-Ended, Current-Mode
T
/C
T
T
to the 5V reference (REF) and C
again. The oscillator’s period will be the
T
t
D
/C
T
t
______________________________________________________________________________________
C
4 88
to GND. REF charges C
f
OSC
.
= 0.57 x R
R
T
R
OSC
t
C
T
C
T
1
MAX5095_Feedback
1 8 10
t
). For the MAX5094B/
.
T
D
10
T
SW
x C
3
is allowed to charge
T
) is the same as the
T
/C
T
3
then discharges
T
T
(see R
is connected
Oscillator
T
T
through R
. Calculate
T
’s voltage
T
T
and C
is con-
T
T
REF is a 5V reference output that can source 20mA.
Bypass REF to GND with a 0.1µF capacitor.
The MAX5094/MAX5095 include a fast current-limit com-
parator to terminate the ON cycle during an overload or a
fault condition. The current-sense resistor (R
ed between the source of the MOSFET and GND, sets
the current limit. The CS input has a voltage trip level
(V
MAX5095_). Use the following equation to calculate R
I
the MOSFET. When the voltage produced by this current
(through the current-sense resistor) exceeds the current-
limit comparator threshold, the MOSFET driver (OUT) will
turn the switch off within 60ns. In most cases, a small RC
filter is required to filter out the leading-edge spike on the
sense waveform. Set the time constant of the RC filter at
50ns. Use a current transformer to limit the losses in the
current-sense resistor and achieve higher efficiency
especially at low input-voltage operation.
SYNC is a bidirectional input/output that outputs a syn-
chronizing pulse and accepts a synchronizing pulse
from other MAX5095A/MAX5095Bs (see Figures 7 and
9). As an output, SYNC is an open-drain p-channel
MOSFET driven from the internal oscillator and requires
an external pulldown resistor (R
and 5k . As an input, SYNC accepts the output pulses
from other MAX5095A/MAX5095Bs.
Synchronize multiple MAX5095A/MAX5095Bs by con-
necting their SYNC pins together. All devices connected
together will synchronize to the one operating at the
highest frequency. The rising edge of SYNC will precede
the rising edge of OUT by approximately the discharge
time (t
pulse width of the SYNC output is equal to the time
required to discharge the stray capacitance at SYNC
through R
R
P-P
T
CS
/C
Synchronization (MAX5095A/MAX5095B)
is the peak current in the primary that flows through
T
) of 1V (MAX5094A/B) or 0.3V (MAX5094C/D,
D
such that the minimum discharge time t
) of the oscillator (see the Oscillator section). The
SYNC
PWM Controllers
plus the C
R
CS
T
I
V
P P
discharge time t
CS
Reference Output
SYNC
Current Limit
) between 500
CS
D
), connect-
D
is 200ns.
. Adjust
SYNC
CS
15
: