AIC1848 Просмотр технического описания (PDF) - Analog Intergrations

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производитель

AIC1848

Regulated 5V Charge Pump In SOT-23

Analog Intergrations 

AIC1848

VIN

RDS-ON-Q2

VOUT

Q1

CIN

ESR

COUT

RDS-ON-Q3

IOFF

CFLY

Q4

Fig. 13 The off state of charge pump circuit

External Capacitor Selection

Three external capacitors, CIN, COUT and CFLY,

determine AIC1848 performances. Optimum

performance can be obtained by using low ESR

ceramic capacitors. Due to high ESR, tantalum

and aluminum capacitors are not recommended

for charge pump application.

To reduce noise and ripple, low ESR ceramic

capacitor is recommended for CIN and COUT. The

value of COUT determines the amount of output

ripple voltage. An output capacitor with larger

value results in smaller ripple.

CFLY is critical for the charge pump. The larger

CFLY is, the larger output current and smaller

ripple voltage obtain. However, large CIN and

COUT are required when large CFLY applies. The

ratio of CIN (as well as COUT) to CFLY should be

approximately 10:1.

Layout Considerations

Due to the switching frequency and high transient

current of AIC1848, careful consideration of PCB

layout is necessary. To achieve the best

performance of AIC1848, minimize the distance

between every two components and also

minimize every connection length with a

maximum trace width. Make sure each device

connects to immediate ground plane. Fig. 14 to

Fig. 16 show the recommended layout.

Fig. 14 Top layer

Fig. 15 Bottom layer

Fig. 16 Top-over layer

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