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參數(shù)資料
| 型號： | MAX5021EUA |
| 廠商： | MAXIM INTEGRATED PRODUCTS INC |
| 元件分類： | 穩(wěn)壓器 |
| 英文描述： | Current-Mode PWM Controllers for Isolated Power Supplies |
| 中文描述： | 0.25 A SWITCHING CONTROLLER, 290 kHz SWITCHING FREQ-MAX, PDSO8 |
| 封裝： | MICRO MAX PACKAGE-8 |
| 文件頁數(shù)： | 5/11頁 |
| 文件大小： | 240K |
| 代理商： | MAX5021EUA |
Detailed Description
The 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, R
S
, (series combination of
R
1
and R
2
) 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 R
S
to 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.
Startup
Figure 2 shows the voltages on V
IN
and V
CC
during
startup. Initially, both V
IN
and V
CC
are 0V. After the line
voltage is applied, C2 charges through the startup
resistor, R
S
, 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 V
CC
voltage reaches approximately 9.5V,
while the voltage across C2 continues rising until it
reaches the wakeup level of 24V. Once V
IN
exceeds
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 V
IN
drops 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 Considerations
The V
IN
bypass 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, V
IN
will drop below 10V because
M
Current-Mode PWM Controllers for Isolated
Power Supplies
_______________________________________________________________________________________
5
Pin Description
PIN
SOT23
PDIP
μ
MAX
NAME
FUNCTION
1
8
CS
C ur ent S ense C onnecti on for P WM Reg ul ati on and Over cur ent P otecti on. The cur ent- m
com p ar ator thr eshol d i s i nter nal y set to 0.6V
2
3
7
6
GND
NDRV
Power-Supply Ground
External N-Channel MOSFET Gate Connection
4
3
V
CC
Gate Drive Supply. Internally regulated down from V
IN
. Decouple with a 10nF or larger
capacitor to GND.
5
2
V
IN
IC Supply. Decouple with a 10nF or larger capacitor to GND. Connect a startup resistor
(R
s
) from the input supply line to V
IN
. Connect to bias winding through diode rectifier.
See
Typical Operating Circuit
.
6
1
OPTO
Optocoupler Transistor Collector Connection. Connect emitter of optocoupler to GND.
The OPTO has an internal pullup resistor with a typical value of 6.2k
.
No Connection. Do not make connections to these pins.
—
4, 5
N.C.
相關(guān)PDF資料 |
PDF描述 |
|---|---|
| MAX5021 | Current-Mode PWM Controllers for Isolated Power Supplies |
| MAX5021EPA | Current-Mode PWM Controllers for Isolated Power Supplies |
| MAX5021EUT | Current-Mode PWM Controllers for Isolated Power Supplies |
| MAX5022 | Current-Mode PWM Controllers for Isolated Power Supplies |
| MAX5022EPA | Current-Mode PWM Controllers for Isolated Power Supplies |
相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| MAX5021EUA+ | 功能描述:電流型 PWM 控制器 for Isolated Power Supplies RoHS:否 制造商:Texas Instruments 開關(guān)頻率:27 KHz 上升時間: 下降時間: 工作電源電壓:6 V to 15 V 工作電源電流:1.5 mA 輸出端數(shù)量:1 最大工作溫度:+ 105 C 安裝風格:SMD/SMT 封裝 / 箱體:TSSOP-14 |
| MAX5021EUA+T | 功能描述:電流型 PWM 控制器 for Isolated Power Supplies RoHS:否 制造商:Texas Instruments 開關(guān)頻率:27 KHz 上升時間: 下降時間: 工作電源電壓:6 V to 15 V 工作電源電流:1.5 mA 輸出端數(shù)量:1 最大工作溫度:+ 105 C 安裝風格:SMD/SMT 封裝 / 箱體:TSSOP-14 |
| MAX5021EUA-T | 功能描述:電流型 PWM 控制器 for Isolated Power Supplies RoHS:否 制造商:Texas Instruments 開關(guān)頻率:27 KHz 上升時間: 下降時間: 工作電源電壓:6 V to 15 V 工作電源電流:1.5 mA 輸出端數(shù)量:1 最大工作溫度:+ 105 C 安裝風格:SMD/SMT 封裝 / 箱體:TSSOP-14 |
| MAX5021EUT | 制造商:Maxim Integrated Products 功能描述:LOW-POWER CURRENT-MODE PWM CONTROL - Cut Tape Product |
| MAX5021EUT+ | 制造商:Maxim Integrated Products 功能描述:CURRENT MODE PWM CNTRLR 250MA 6PIN SOT-23 - Rail/Tube |
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