参数资料
型号: LA5752
元件分类: 稳压器
英文描述: 3 A SWITCHING REGULATOR, 72 kHz SWITCHING FREQ-MAX, PZFM5
封装: TO-220, 5 PIN
文件页数: 4/5页
文件大小: 66K
代理商: LA5752
LA5752
No.A0947-4/5
Td =
=
= 28.2 msec
C
× V
i
1
× 0.62
22
Tss =
=
C
× VPWM × PWMduty
i
C
× 0.88 × PWMduty
22
A
1.5V
0.62V
PWM wave
Tss =
= 10.8msec
1
× 0.88V × 0.27
22
A
PWMduty =
= 27%
VOUT + VF
VIN - Vsat + VF
Description of Functional Settings
1.Start delay function
The SS pin has the internally-connected 22
A (typ) constant-current supply. When the voltage of SS pin exceeds the
threshold voltage, the regulator starts operation. As the threshold is 0.62V(typ), the start delay time can be calculated
as follows:
ex. For setting at 1
F
2.Soft start function
The internal PWM waveform has the voltage value as shown in the right.
If down-conversion from the voltage of VIN = 20V to 5V output to be made,
for example, the PWM-ON duty has the value as shown below.
(Note that calculation is made with Vsat = 1V and VF = 0.2V)
The output voltage of error amplifier, which is 5V, is the value with PWM = 27%, as calculated in the above equation,
so that this voltage is determined as follows:
Ver = (
VPWM) × PWMduty + VPWML = 0.88V × 0.27 + 0.62V = 0.86V
(
VPWM is the PWM amplitude value or 0.88V(typ) while VPWML is the lower limit voltage of PWM
waveform or 0.62V(typ))
SS pin and error amplifier output voltages are designed to prefer the lower voltages, so that VOUT will reach the
designed regulation voltage in timing when the SS pin voltage exceeds the error amplifier output. Therefore, the soft
strt time is calculated as follows:
For the set conditions of C = 1
F and PWMduty = 27%:
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