参数资料
| 型号： | SC412AMLTRT |
| 厂商： | Semtech |
| 文件页数： | 15/22页 |
| 文件大小： | 0K |
| 描述： | IC REG CTRLR BUCK PWM 16-MLP |
| 标准包装： | 1 |
| PWM 型： | 控制器 |
| 输出数： | 1 |
| 频率 - 最大： | 325kHz |
| 占空比： | 90% |
| 电源电压： | 3 V ~ 25 V |
| 降压： | 是 |
| 升压： | 无 |
| 回扫： | 无 |
| 反相： | 无 |
| 倍增器： | 无 |
| 除法器： | 无 |
| Cuk： | 无 |
| 隔离： | 无 |
| 工作温度： | -40°C ~ 85°C |
| 封装/外壳： | 16-MLP |
| 包装： | 标准包装 |
| 其它名称： | SC412AMLDKR |
NOT RECOMMENDED FOR NEW DESIGN
POWER MANAGEMENT
Applications Information (continued)
SC412A
by increasing the duty cycle (more time is spent drawing
energy from VBAT as losses increase). Since the on-time
is constant for a given VOUT/VBAT combination, the way
to increase duty cycle is to gradually shorten the off-time.
The net effect is that switching frequency increases slightly
with increasing load.
The typical operating frequency is 325kHz. It is possible to
raise the frequency by placing a resistor divider between
the output and the VOUT pin, see Figure 7. This reduces
the voltage at the VOUT pin which is used to generate the
on-time according to the previous equation. Note that
It is also possible to lower the frequency using a resistive
divider to the 5V bias supply, see Figure 3. This raises the
voltage at the VOUT pin which will increase the on-time.
Note that this results in a small leakage path from the 5V
supply to the output voltage. The resistor values should be
fairly large (>50kOhm) large to prevent the output voltage
from drifting up during shutdown conditions. Note that
the feedback resistors act as a dummy load to limit how
far the output can rise.
The new operating frequency is approximated by the
equation:
this places a small minimum load on the output. The new
frequency is approximated by the following equation:
FREQ (kHz) = 325 ? ((R1 + R2) / (R1 + R2 ? VCC/VOUT))
FREQ (kHz) = 325 ? (1 + R1/R2)
VCC
V LX
L
ESR
Power Output
V OUT
R1
V LX
L
ESR
R1
Power Output
V OUT
R2
C OUT
+
R2
1nF
pin 10
(VOUT)
C OUT
+
1nF
pin 10
(VOUT)
Figure 8.
Figure 7.
? 2006 Semtech Corp.
15
www.semtech.com
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