參數(shù)資料
型號: XC9237C1CCEL
廠商: TOREX SEMICONDUCTOR LTD.
英文描述: 600mA Driver Tr. Built-In, Synchronous Step-Down DC/DC Converters
中文描述: 600mA的驅(qū)動程序圖。內(nèi)置的同步降壓DC / DC轉(zhuǎn)換器
文件頁數(shù): 10/28頁
文件大小: 774K
代理商: XC9237C1CCEL
10/28
XC9235/XC9236/XC9237
Series
OPERATIONAL DESCRIPTION (Continued)
<Short-Circuit Protection>
The short-circuit protection circuit monitors the internal R1 and R2 divider voltage from the V
OUT
pin (refer to FB point in
the block diagram shown in the previous page). In case where output is accidentally shorted to the Ground and when
the FB point voltage decreases less than half of the reference voltage (Vref) and a current more than the I
LIM
flows to
the driver transistor, the short-circuit protection quickly operates to turn off and to latch the driver transistor. In latch
mode, the operation can be resumed by either turning the IC off and on via the CE/MODE pin, or by restoring power
supply to the V
IN
pin.
When sharp load transient happens, a voltage drop at the V
OUT
is propagated to the FB point through C
FB
, as a result,
short circuit protection may operate in the voltage higher than 1/2 V
OUT
voltage.
<U.V.L.O. Circuit>
When the V
IN
pin voltage becomes 1.4V or lower, the P-channel output driver transistor is forced OFF to prevent false
pulse output caused by unstable operation of the internal circuitry. When the V
IN
pin voltage becomes 1.8V or higher,
switching operation takes place. By releasing the U.V.L.O. function, the IC performs the soft start function to initiate
output startup operation. The soft start function operates even when the V
IN
pin voltage falls momentarily below the
U.V.L.O. operating voltage. The U.V.L.O. circuit does not cause a complete shutdown of the IC, but causes pulse output
to be suspended; therefore, the internal circuitry remains in operation.
<PFM Switch Current>
In PFM control operation, until coil current reaches to a specified level (I
PFM
), the IC keeps the P-ch MOSFET on. In this
case, time that the P-ch MOSFET is kept on (TON) can be given by the following formula.
TON= L
I
PFM
(V
IN
V
OUT
)
I
PFM
<Maximum I
PFM
Limit>
In PFM control operation, the maximum duty ratio (MAXI
PFM
) is set to 200% (TYP.). Therefore, under the condition that
the duty increases (e.g. the condition that the step-down ratio is small), it’s possible for P-ch MOSFET to be turned off even
when coil current doesn’t reach to I
PFM
.
I
PFM
IPFM
Ton
Lx
I Lx
IPFM
0mA
IPFM
IPFM
0mA
Lx
I Lx
FOSC
Maxumum IPFM Current
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相關(guān)代理商/技術(shù)參數(shù)
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XC9237C1CCER 制造商:TOREX 制造商全稱:Torex Semiconductor 功能描述:600mA Driver Tr. Built-In, Synchronous Step-Down DC/DC Converters
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