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参数资料
| 型号： | L5970ADTR |
| 厂商： | STMICROELECTRONICS |
| 元件分类： | 稳压器 |
| 英文描述： | 1.8 A SWITCHING REGULATOR, 500 kHz SWITCHING FREQ-MAX, PDSO8 |
| 封装： | SO-8 |
| 文件页数： | 8/11页 |
| 文件大小： | 139K |
| 代理商： | L5970ADTR |
L5970AD
6/11
3.4 CURRENT PROTECTION
The L5970AD has two current limit protections, pulse by pulse and frequency fold back.
The schematic of the current limitation circuitry for the pulse by pulse protection is shown in figure 7.
The output power PDMOS transistor is split in two parallel PDMOS. The smallest one has a resistor in series,
RSENSE. The current is sensed through Rsense and if reaches the threshold, the mirror is unbalanced and the
PDMOS is switched off until the next falling edge of the internal clock pulse.
Due to this reduction of the ON time, the output voltage decreases.
Since the minimum switch ON time (necessary to avoid false overcurrent signal) is not enough to obtain a suf-
ficiently low duty cycle at 500KHz, the output current, in strong overcurrent or short circuit conditions, could in-
crease again. For this reason the switching frequency is also reduced, so keeping the inductor current under its
maximum threshold. The Frequency Shifter (see fig. 6) depends on the feedback voltage. As the feedback volt-
age decreases (due to the reduced duty cycle), the switching frequency decreases too.
Figure 7. Current Limitation Circuitry
3.5 ERROR AMPLIFIER
The voltage error amplifier is the core of the loop regulation. It is a transconductance operational amplifier whose
non inverting input is connected to the internal voltage reference (1.235V), while the inverting input (FB) is con-
nected to the external divider or directly to the output voltage. The output (COMP) is connected to the external
compensation network.
The uncompensated error amplifier has the following characteristics:
The error amplifier output is compared with the oscillator sawtooth to perform PWM control.
3.6 PWM COMPARATOR AND POWER STAGE
This block compares the oscillator sawtooth and the error amplifier output signals generating the PWM
signal for the driving stage.
The power stage is a very critical block cause it has to guarantee a correct turn on and turn off of the PD-
MOS.
Transconductance
2300
S
Low frequency gain
65dB
Minimum sink/source voltage
1500
A/300A
Output voltage swing
0.4V/3.65V
Input bias current
2.5
A
DRIVER
NOT
A1
PWM
VCC
OUT
A1/A2=95
IL
RSENSE
D00IN1134
IOFF
I
RTH
A2
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相关代理商/技术参数 |
参数描述 |
|---|---|
| L5970D | 功能描述:直流/直流开关调节器 1.2 to 35V Step-Down RoHS:否 制造商:International Rectifier 最大输入电压:21 V 开关频率:1.5 MHz 输出电压:0.5 V to 0.86 V 输出电流:4 A 输出端数量: 最大工作温度: 安装风格:SMD/SMT 封装 / 箱体:PQFN 4 x 5 |
| L5970D_07 | 制造商:STMICROELECTRONICS 制造商全称:STMicroelectronics 功能描述:Up to 1A step down switching regulator |
| L5970D_0710 | 制造商:STMICROELECTRONICS 制造商全称:STMicroelectronics 功能描述:Up to 1A step down switching regulator |
| L5970D013 | 制造商:STMICROELECTRONICS 制造商全称:STMicroelectronics 功能描述:UP TO 1A STEP DOWN SWITCHING REGULATOR |
| L5970D013TR | 功能描述:直流/直流开关调节器 1.2 to 35V Step-Down RoHS:否 制造商:International Rectifier 最大输入电压:21 V 开关频率:1.5 MHz 输出电压:0.5 V to 0.86 V 输出电流:4 A 输出端数量: 最大工作温度: 安装风格:SMD/SMT 封装 / 箱体:PQFN 4 x 5 |
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