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参数资料
| 型号： | DS1670S |
| 厂商： | DALLAS SEMICONDUCTOR |
| 元件分类： | Timer or RTC |
| 英文描述： | 0 TIMER(S), REAL TIME CLOCK, PDSO20 |
| 封装： | SOIC-20 |
| 文件页数： | 2/16页 |
| 文件大小： | 312K |
| 代理商： | DS1670S |
MAX774/MAX775/MAX776
the current limit for the first two pulses is set to one-half
the peak current limit. If those pulses bring the output
voltage into regulation, the voltage comparator keeps
the MOSFET off, and the current limit remains at one-half
the peak current limit. If the output voltage is out of
regulation after two consecutive pulses, the current limit
for the next pulse will equal the full current limit.
With heavy loads, the MOSFET first switches twice at
one-half the peak current value. Subsequently, it stays
on until the switch current reaches the full current limit,
and then turns off. After it is off for 2.3s, the MOSFET
switches on once more, and remains on until the switch
current again reaches its limit. This cycle repeats until
the output is in regulation.
A benefit of this control scheme is that it is highly effi-
cient over a wide range of input/output ratios and load
currents. Additionally, PFM converters do not operate
with constant-frequency switching, and have relaxed
stability criterion (unlike PWM converters). As a result,
their external components require smaller values.
With PFM converters, the output voltage ripple is not
concentrated at the oscillator frequency (as it is with
PWM converters). For applications where the ripple fre-
quency is important, the PWM control scheme must be
used. However, for many other applications, the smaller
capacitors and lower supply current of the PFM control
scheme make it the better choice. The output voltage
ripple with the MAX774/MAX775/MAX776 can be held
quite low. For example, using the circuit of Figure 2,
only 100mV of output ripple is produced when generat-
ing a -5V at 1A output from a +5V input.
Bootstrapped vs.
Nonbootstrapped Operation
Figures 2 and 3 are the standard application circuits
for bootstrapped mode, and Figure 4 is the circuit for
nonbootstrapped mode. Since EXT is powered by OUT,
using bootstrapped or nonbootstrapped mode will
directly affect the gate drive to the FET. EXT swings
from V+ to VOUT. In bootstrapped operation, OUT is
-5V/-12V/-15V or Adjustable, High-Efficiency,
Low IQ Inverting DC-to-DC Controllers
10
______________________________________________________________________________________
MAX774
MAX775
MAX776
OUT
V+
SHDN
CS
FB
EXT
GND
P
7
8
C2
0.1
F
R1
0.07
C1
150
F
6
5
2
3
1
REF
4
Q1
Si9435
1N5822/
MBR340
L1
22
H
C4
*
VIN
C3
0.1
F
VOUT
* MAX774 = 330F, 10V
MAX775, MAX776 = 120
F, 20V
PRODUCT
MAX774
MAX775
MAX776
OUTPUT
VOLTAGE (V)
-5
-12
-15
INPUT
VOLTAGE (V)
3 to 15
3 to 8
3 to 5
OUTPUT
CURRENT (A)
1
0.5
0.4
NOTE: Si9435 HAS VGS OF 20V MAX
MAX774
MAX775
MAX776
OUT
V+
SHDN
CS
FB
EXT
GND
P
7
8
R2
R3
0.07
C1
150
F
6
5
2
3
1
REF
4
Q1
Si9435
1N5822/
MBR340
L1
22
H
C4
*
VIN
C3
0.1
F
VOUT
C2
0.1
F
R1
* MAX774 = 330F, 10V
MAX775, MAX776 = 120
F, 20V
Figure 2. Bootstrapped Connection Using Fixed Output
Voltages
Figure 3. Bootstrapped Connection Using External Feedback
Resistors
Figure 4. Nonbootstrapped Operation (VIN > 4.5V)
MAX774
MAX775
MAX776
OUT
V+
SHDN
CS
FB
EXT
GND
P
7
8
R2
R3
0.07
C1
150
F
6
5
2
3
1
REF
4
Q1
Si9435
1N5822/
MBR340
L1
22
H
C4
*
VIN
C3
0.1
F
VOUT
C2
0.1
F
R1
* MAX774 = 330F, 10V
MAX775, MAX776 = 120
F, 20V
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相关代理商/技术参数 |
参数描述 |
|---|---|
| DS1670S+ | 功能描述:实时时钟 Portable System Controller RoHS:否 制造商:Microchip Technology 功能:Clock, Calendar. Alarm RTC 总线接口:I2C 日期格式:DW:DM:M:Y 时间格式:HH:MM:SS RTC 存储容量:64 B 电源电压-最大:5.5 V 电源电压-最小:1.8 V 最大工作温度:+ 85 C 最小工作温度: 安装风格:Through Hole 封装 / 箱体:PDIP-8 封装:Tube |
| DS1671H | 制造商:未知厂家 制造商全称:未知厂家 功能描述:Dual Clock Driver |
| DS1671J-8 | 制造商:未知厂家 制造商全称:未知厂家 功能描述:Dual Clock Driver |
| DS-1671ZJ | 制造商:Hikvision USA 功能描述:4" Indoor Ceiling Embedded Mount |
| DS1672 | 制造商:DALLAS 制造商全称:Dallas Semiconductor 功能描述:Low Voltage Serial Timekeeping Chip |
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