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| 型号： | AS1339 EB |
| 厂商： | ams |
| 文件页数： | 20/26页 |
| 文件大小： | 0K |
| 描述： | BOARD EVAL AS1339 |
| 标准包装： | 1 |
| 主要目的： | DC/DC，LDO 步降 |
| 输出及类型： | 3，非隔离 |
| 输出电压： | 0.8 ~ 3.75 V，2.85V，2.85V |
| 电流 - 输出： | 650mA |
| 输入电压： | 2.7 ~ 5.5 V |
| 稳压器拓扑结构： | 降压 |
| 频率 - 开关： | 2MHz |
| 板类型： | 完全填充 |
| 已供物品： | 板 |
| 已用 IC / 零件： | AS1339 |
AS1339
Datasheet - A p p l i c a t i o n I n f o r m a t i o n
Capacitor Selection for LDO’s
Input Capacitor
The capacitor for the LDO Input should have at least a value of the sum of the output capacitors of LDO1 and LDO2.
With a larger input capacitance and lower ESR a better noise rejection and line transient response can be achieved.
Output Capacitor
For the LDO outputs the capacitor value depends on the needed load current. For a stable operation with rated maxi-
mum load currents a minimum output capacitor of 1μF is recommended. At light loads of 10mA or less a 0.1μF capac-
itor is sufficient. With larger output capacitance a reduced output noise, improved load-transient response, better
stability and power-supply rejection can be achieved.
Table 7. Recommended Capacitors for the LDO’s
Name
C IN2 , C LDO1 ,
C LDO2
Part Number
C0402C104K4RAC
GRM155R61A105KE15
C
100nF
1μF
Voltage
16V
10V
Type
X7R
X5R
Size
0402
0402
Manufacturer
KEMET
Murata
Inductor Selection
For most applications the value of the external inductor should be in the range of 1.5μH to 4.7μH as the inductor value
has a direct effect on the ripple current. The selected inductor must be rated for its DC resistance and saturation cur-
rent. The inductor ripple current ( Δ I L ) decreases with higher inductance and increases with higher V IN to V OUT .
In Equation (EQ 3) the maximum inductor current in PWM mode under static load conditions is calculated. The satura-
tion current of the inductor should be rated higher than the maximum inductor current as calculated with Equation (EQ
4) . This is recommended because the inductor current will rise above the calculated value during heavy load tran-
sients.
The inductor current ripple Δ I L (see EQ 3) is defined by the slope of the current (dI / dt) (see EQ 1) multiplied by the
Figure 51. Ripple Current Diagram
I L
I Lmax
I OUTmax
t ON
dI
dt
1/f
Δ I L
t
dI -
V IN – V OUT
---- = ----------------------------
dt L
(EQ 1)
t ON = DutyCycle × ---
V OUT
1
f
DutyCycle = -------------
V IN
(EQ 2)
Revision 1.05
19 - 25
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| AS133R0JLF | 制造商:TT Electronics / IRC 功能描述:AS133R0JLF |
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