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參數(shù)資料
| 型號： | SG3524 |
| 廠商： | Microsemi Corporation |
| 英文描述： | REGULATING PULSE WIDTH MODULATOR |
| 中文描述： | 調控脈寬調制器 |
| 文件頁數(shù)： | 5/5頁 |
| 文件大小： | 125K |
| 代理商： | SG3524 |
Philips Semiconductors
Product specification
SG3524
SMPS control circuit
1994 Aug 31
5
One final point on the compensation terminal is that this is also a
convenient place to insert any programming signal which is to
override the error amplifier. Internal shutdown and current limit
circuits are connected here, but any other circuit which can sink
200
μ
A can pull this point to ground, thus shutting off both outputs.
While feedback is normally applied around the entire regulator, the
error amplifier can be used with conventional operational amplifier
feedback and is stable in either the inverting or non-inverting mode.
Regardless of the connections, however, input common-mode limits
must be observed or output signal inversions may result. For
conventional regulator applications, the 5V reference voltage must
be divided down as shown in Figure 8. The error amplifier may also
be used in fixed duty cycle applications by using the unity gain
configuration shown in the open-loop test circuit.
Current Limiting
The current limiting circuitry of the SG3524 is shown in Figure 9.
By matching the base-emitter voltages of Q1 and Q2, and assuming
a negligible voltage drop across R
1
:
Threshold=V
BE
(Q1)+I
1
R
2
-V
BE
(Q2)
=I
1
R
2
200mV
Although this circuit provides a relatively small threshold with a
negligible temperature coefficient, there are some limitations to its
use, the most important of which is the
±
1V common-mode range
which requires sensing in the ground line. Another factor to consider
is that the frequency compensation provided by R
1
C
1
and Q1
provides a roll-off pole at approximately 300Hz.
Since the gain of this circuit is relatively low, there is a transition
region as the current limit amplifier takes over pulse width control
from the error amplifier. For testing purposes, threshold is defined as
the input voltage required to get 25% duty cycle with the error
amplifier signaling maximum duty cycle.
In addition to constant current limiting, Pins 4 and 5 may also be
used in transformer-coupled circuits to sense primary current and to
shorten an output pulse, should transformer saturation occur.
Another application is to ground Pin 5 and use Pin 4 as an additional
shutdown terminal: i.e., the output will be off with Pin 4 open and on
when it is grounded. Finally, foldback current limiting can be
provided with the network of Figure 10. This circuit can reduce the
short-circuit current (I
SC
) to approximately one-third the maximum
available output current (I
MAX
).
VOLTAGES
2
1
OUTPUT
GND
+
–
V
REF
R
1
R
2
5k
5k
OUTPUT
2
1
POSITIVE
GND
+
–
5k
5k
V
REF
R
1
R
2
SL00181
Figure 8. Error Amplifier Biasing Circuits
+
–
t
1
9
4
5
R
1
R
1
COMPARATOR
AERROR
RAMP
SENSE
Q1
Q2
C
1
SL00182
Figure 9. Current Limiting Circuitry of the SG3524
NOTE:
Foldback current limiting can be used to reduce power dissipation
under shorted output conditions.
IMAX
1
RS
VTH
V0R2
R1
R2
ISC
VTH
RS
where
V
TH
= 200mV
5
4
V
O
= 5V
S
A
/S
B
R
1
R
2
R
S
+
–
SENSE
SL00183
Figure 10. Foldback Current Limiting
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| SG3524D | REGULATING PULSE WIDTH MODULATOR |
| SG3524J | Regulating Pulse Width Modulator |
| SG3524N | Regulating Pulse Width Modulator |
| SG3524 | Regulating Pulse Width Modulator |
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相關代理商/技術參數(shù) |
參數(shù)描述 |
|---|---|
| SG3524B | 制造商:MICROSEMI 制造商全稱:Microsemi Corporation 功能描述:REGULATING PULSE WIDTH MODULATOR |
| SG3524BDW | 功能描述:IC REG CTRLR BUCK PWM VM 16-SOIC RoHS:是 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - DC DC 切換控制器 系列:- 特色產品:LM3753/54 Scalable 2-Phase Synchronous Buck Controllers 標準包裝:1 系列:PowerWise® PWM 型:電壓模式 輸出數(shù):1 頻率 - 最大:1MHz 占空比:81% 電源電壓:4.5 V ~ 18 V 降壓:是 升壓:無 回掃:無 反相:無 倍增器:無 除法器:無 Cuk:無 隔離:無 工作溫度:-5°C ~ 125°C 封裝/外殼:32-WFQFN 裸露焊盤 包裝:Digi-Reel® 產品目錄頁面:1303 (CN2011-ZH PDF) 其它名稱:LM3754SQDKR |
| SG3524BDW-TR | 制造商:Microsemi Corporation 功能描述:Voltage Mode PWM Controller 19V 100mA 16-Pin SOWB T/R |
| SG3524BJ | 制造商:Microsemi Corporation 功能描述:SG3524BJ - Bulk |
| SG3524BN | 制造商:Microsemi Corporation 功能描述:Voltage Mode PWM Controller 19V 100mA 16-Pin PDIP 制造商:Microsemi Corporation 功能描述:VOLT MODE PWM CNTRLR 19V 100MA 16PDIP - Rail/Tube 制造商:Microsemi 功能描述:Voltage Mode PWM Controller 19V 100mA 16-Pin PDIP |
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