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參數(shù)資料
| 型號(hào)： | TC38C43CPA |
| 廠商： | TelCom Semiconductor, Inc. |
| 英文描述： | BiCMOS CURRENT MODE PWM CONTROLLERS |
| 中文描述： | 的BiCMOS電流模式PWM控制器 |
| 文件頁數(shù)： | 5/7頁 |
| 文件大?。?/td> | 83K |
| 代理商： | TC38C43CPA |
4-97
TELCOM SEMICONDUCTOR, INC.
7
6
5
4
3
1
2
8
TC18C43
TC28C43
TC38C43
BiCMOS CURRENT MODE
PWM CONTROLLERS
Dead Time
The value of R
T
has an effect on the discharge rate but
the primary consideration is the value of C
T
. The time
required to discharge the capacitor is approximately 1000
C
T
.
Undervoltage Lockout Range
The TCx8C43 PWM Controller is used where wide
ranges of input voltage is not required. The range from
starting V
in
voltage threshold to under voltage threshold is
approximately 9.5% of the starting voltage. The typical start-
up voltage is 8.4V and dropout voltage is 7.6V. This range
is used most in DC-to-DC converter applications.
Duty Cycle Limit
The TCx8C43 PWM Controller has a duty cycle limit
maximum of 99%. The oscillator is running at the same
frequency as the output.
Current is sensed through voltage drop across resistor
RS. A small RC filter may be required to suppress switching
transient. This voltage enters PWM Controller at I
SENSE
,
pin 5. A voltage of 0.4 V is added before this is fed into PWM
Comparator (+) input. The PWM Comparator (–) input
senses the voltage feedback error amp output with a limit
buffer that limits this voltage to 1.4V maximum. This limit
buffer limits the peak current across RS to a maximum of
0.95V. In normal operation, the error amplifier controls the
current limit threshold.
Shutdown can be accomplished by either pulling I
SENSE
above 1 volt or pulling CMPTR, pin 1 to GND. This will set the
PWM latch so that the output will remain low until the next
clock pulse after the shutdown condition is removed.
SHUTDOWN METHODS
TCx8C43
VON = 8.4V
VOFF = 7.6V
IS
7.6V
8.4 V
1mA
170
μ
A
VDD
VIN
TCx8C43
ERROR AMP
+
–
LIMIT BUFFER
+
–
1.4V
2R
R
GND
+
–
C
R
ISENSE
5
0.4V
PWM
COMPARATOR
9
RS
PEAK CURRENT (IS) FORMULA:
IS =
0.95V
RS
CURRENT SENSE CIRCUIT
ISENSE
5
TCx38C43
VREF
SHUTDOWN
14
TO CURRENT
SENSE RESISTOR
5k
5.1k
9
TCx38C43
SHUTDOWN
ANALOG
GND
CMPTR
1
BENCH TEST OPERATIONAL SIMULATION
The timing ramp (R
T
/C
T
) is buffered by the emitter
fullpower and fed back to the I
SENSE
input. This ramp
simulates the dI/dT current ramp which would flow through
the primary of the transformer. The output voltage of the
power supply is simulated by feeding some of the reference
voltage into V
FB
. The combination of the two levels deter-
mined the operating characteristics of the current mode
controller.
UNDERVOLTAGE LOCKOUT RANGE
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| TC38C43CPD | 制造商:TELCOM 制造商全稱:TelCom Semiconductor, Inc 功能描述:BiCMOS CURRENT MODE PWM CONTROLLERS |
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| TC38C46CPE | 制造商:TELCOM 制造商全稱:TelCom Semiconductor, Inc 功能描述:CMOS CURRENT MODE PWM CONTROLLER |
| TC38C47 | 制造商:TELCOM 制造商全稱:TelCom Semiconductor, Inc 功能描述:CMOS CURRENT MODE PWM CONTROLLER |
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