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參數(shù)資料
| 型號(hào)： | SP6121EB |
| 英文描述： | Demo Board Manual |
| 中文描述： | 演示板手冊(cè) |
| 文件頁數(shù)： | 6/16頁 |
| 文件大?。?/td> | 358K |
| 代理商： | SP6121EB |
Date: 5/25/04
SP6121 Low Voltage, Synchronous Step Down PWM Controller Copyright 2004 Sipex Corporation
6
clamp and then gradually charges preventing
the error amplifier from forcing the loop to
maximum duty cycle. As the COMP voltage
crosses about 1V (valley voltage of the PWM
ramp), the driver begins to switch the high side
MOSFET with narrow pulses in an effort to
keep the converter output regulated . The SP6121
operates at low duty cycle as the COMP voltage
increases above 1V. As the error amp reference
ramps upward, the driver pulses widen until a
steady state value is reached and the output
voltage is regulated to the final value ending the
soft start charge cycle.
Hiccup Mode
When the converter enters a fault mode, the
SP6121 holds the high side and low side
MOSFETs off for a finite period of time. Pro-
vided that the SP6121 is enabled, this time is set
by the internal charge of the SS capacitor. In the
event of an over-current condition, the current
sense comparator sets the fault latch, which in
turn discharge the internal SS capacitor, the
COMP pin and holds the output drivers off.
During this condition, the SP6121 stays off for
the time it takes to discharge the COMP pin
down below the 0.3V shutdown threshold. As
soon as the COMP pin reaches 0.3V, the fault
latch is reset and the SP6121 is allowed to
attempt restart just like during a normal soft start
cycle. The COMP pin has to charge back to 1V
before any output switching can take place. At
this point, the regulator attempts to restart nor-
mally by delivering short gate pulses to the
output switches. If the over-current condition
persists, the regulator will be kept off for the
total time that it takes to charge the internal soft-
start capacitor to within 1V from the input
supply voltage V
CC
plus the time required by the
COMP voltage to cross the 1V threshold. This
total time is typically several milli-seconds and
minimizes thermal stress to the regulator com-
ponents as the over-current condition persists.
The waveforms that describe the hiccup mode
operation are shown in Figure 2.
160 mV
3 V
0 V
1.0 V
0V
V
(VCC)
PDRV
Voltage
V
(ISET)
-V
(ISENSE)
TIME
0 V
0.3 V
COMP
Voltage
Figure 2. SP6121 Hiccup mode waveforms
dVss/dt = 0.4V/ms
1.25V
I(L)
TIME
0.3 V
0 V
0.7 V
1 V
V
OUT
= V
(REF)
* (1+R1/R2)
COMP
Internal SS
Voltage
0 V
SWN
Voltage
FAULT
Current
Inductor
0 A
Voltage
Reference
Error Amp
0 V
V(V
CC
)
0 V
V(V
CC
)
Figure 1. SP6121 Soft Start Waveforms
THEORY OF OPERATION: continued
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| SP6122 | 制造商:SIPEX 制造商全稱:Sipex Corporation 功能描述:Low Voltage, Micro 8, PFET, Buck Controller Ideal for 1A to 5A, Small Footprint, DC-DC Power Converters |
| SP6122_04 | 制造商:SIPEX 制造商全稱:Sipex Corporation 功能描述:Low Voltage, Micro 8, PFET, Buck Controller Ideal for 1A to 5A, Small Footprint, DC-DC Power Converters |
| SP6122ACU | 制造商:Rochester Electronics LLC 功能描述: 制造商:Exar Corporation 功能描述: |
| SP6122ACU/TR | 制造商:Exar Corporation 功能描述: |
| SP6122ACU-1.5 | 制造商:SIPEX 制造商全稱:Sipex Corporation 功能描述:Low Voltage, Micro 8, PFET, Buck Controller Ideal for 1A to 5A, Small Footprint, DC-DC Power Converters |
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