MAX15000AEUB+ Maxim Integrated Products, MAX15000AEUB+ Datasheet - Page 10

• Manufacturer Part Number: MAX15000AEUB+
• Description: IC CNTRLR PWM CURRENT MD 10UMAX
• Manufacturer: Maxim Integrated Products

Specifications of MAX15000AEUB+

• Pwm Type: Current Mode
• Number Of Outputs: 1
• Frequency - Max: 2.5MHz
• Duty Cycle: 50%
• Voltage - Supply: 23.6 V ~ 30 V
• Buck: No
• Boost: Yes
• Flyback: Yes
• Inverting: No
• Doubler: No
• Divider: No
• Cuk: No
• Isolated: Yes
• Operating Temperature: -40°C ~ 85°C
• Package / Case: 10-MSOP, Micro10™, 10-uMAX, 10-uSOP
• Frequency-max: 2.5MHz
• Duty Cycle (max): 50 %
• Output Current: 1000 mA
• Mounting Style: SMD/SMT
• Switching Frequency: 25 KHz to 625 KHz
• Maximum Operating Temperature: + 85 C
• Minimum Operating Temperature: - 40 C
• Synchronous Pin: No
• Topology: Boost
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

threshold), then startup has been accomplished and
sustained operation will commence. If V
9.74V before startup is complete, the device goes back
to low-current UVLO. In this case, increase the value of
C1 to store enough energy to allow for the voltage at
the tertiary winding to build up.
Current-Mode PWM Controllers with
Programmable Switching Frequency
Figure 2. V IN and V CC During Startup When Using the
MAX15000 in Bootstrapped Mode (Figure 1)
Figure 3. UVLO/EN and UFLG Operation Timing
10
______________________________________________________________________________________
V
V
V
UVLO/EN
UFLG
NDRV
100ms/div
SHUTDOWN
LOW
(±1%)
1.23V
MAX15000 fig02
3µs
IN
t
3ms
EXTR
V
2V/div
V
5V/div
0V
drops below
Hi-Z
CC
IN
NDRV SWITCHING
The MAX15000/MAX15001 have an open-drain under-
voltage flag output (UFLG). When used with an opto-
coupler the UFLG output can serve to sequence a
secondary-side controller. An internal 210µs delay
occurs the instant the voltage on UVLO/EN drops
below 1.17V until NDRV stops switching. This allows for
the UFLG output to change state before the MAX15000/
MAX15001 shut down
When the voltage at the UVLO/EN is above the thresh-
old, UFLG is high impedance. When UVLO/EN is below
the threshold, UFLG goes low. UFLG is not affected by
bootstrap UVLO (MAX15000).
The MAX15000/MAX15001 soft-start feature allows the
output voltage to ramp up in a controlled manner, elimi-
nating voltage overshoot. The MAX15000/MAX15001
reference generator that is internally connected to the
error amplifier soft-starts to achieve superior control of
the output voltage under heavy and light load condi-
tions. Soft-start begins after UVLO is deasserted (V
above 21.6V for the MAX15000, V
the MAX15001, and the voltage on UVLO/EN is above
1.23V). The voltage applied to the noninverting node of
the amplifier ramps from 0 to 1.23V in 1984 NDRV
switching cycles. Use the following formula to calculate
the soft-start time (t
where f
output. Figure 4 shows the soft-start regulated output of
a power supply using the MAX15000 during startup.
0.6µs
NDRV
210µs
1.17V (typ)
t
EXTF
LOW
is the switching frequency at the NDRV
SS
t
SS
):
(Figure 3).
=
f
1984
NDRV
SHUTDOWN
UVLO Flag (UFLG)
IN
is above 9.5V for
Soft-Start
IN
is