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參數(shù)資料
| 型號： | RT9203AGS |
| 廠商： | Richtek Technology Corporation |
| 英文描述： | Dual Regulators - Synchronous Buck PWM DC-DC and Linear Controller |
| 中文描述： | 雙穩(wěn)壓器-同步降壓PWM型DC - DC和線性控制器 |
| 文件頁數(shù)： | 14/16頁 |
| 文件大?。?/td> | 228K |
| 代理商： | RT9203AGS |
RT9203/A
Preliminary
14
DS9203/A-10 March 2007
www.richtek.com
Reference Voltage
Because RT9203/A uses a low 35dB gain error amplifier,
as shown in Figure 10. The voltage regulation is
dependent on V
IN
and V
OUT
settings. The FB reference
voltage of 0.8V were trimmed at V
IN
= 5V and V
OUT
=
2.5V. In a fixed V
IN
= 5V application, the FB reference
voltage vs. V
OUT
voltage can be calculated as Figure 11.
Figure 11
Feedback Divider
The reference of RT9203/A is 0.8V. The output voltage can
be set using a resistor-divider as shown in Figure 12. Put
the R1 and R2 as close as possible to FB pin. R2 value
should be less than 1 k
to avoid noise coupling issue.
The C1 capacitor is a speed-up capacitor for reducing output
ripple to meet with the requirement of fast transient load.
Typically a 1nF ~ 0.1
μ
F is enough for C1.
Figure 12
PWM Layout Considerations
MOSFETs switch very fast in efficiency. The speed with
which the current transitions from one device to another
causes voltage spikes across the interconnecting
impedances and parasitic circuit elements. The voltage
spikes can degrade efficiency and radiate noise, that
results in over-voltage stress on devices. Careful the
layout for component placement and printed circuit design
can minimize the voltage spikes induced in the converter.
Consider, as an example, the turn-off transition of the
upper MOSFET prior to turn-off, the upper MOSFET was
carrying the full load current. During turn-off, current stops
flowing in the upper MOSFET and is picked up by the
lower MOSFET or Schottky diode. Any inductance in the
switched current path generates a large voltage spike
during the switching interval. Care with component
selections, layout of the critical components, and use
shorter and wider PCB traces that help in minimizing the
magnitude of voltage spikes.
There are two sets of critical components in a DC-DC
converter using the RT9203/A. The switching power
components are most critical because they switch large
amounts of energy, and as such, they tend to generate
equally large amounts of noise. The critical small signal
components are those connected to sensitive nodes or
those supplying critical bypass current.
The power components and the PWM controller should
be placed firstly. Place the input capacitors, especially the
high-frequency ceramic decoupling capacitors, close to
the power switches. Place the output inductor and output
capacitors between the MOSFETs and the load. Also
locate the PWM controller near by MOSFETs.
+
-EA
-
PWM
R1
56K
R1
1K
+
-
FB
REP
0.8V
RAMP
1.75V
Figure 10
F
Duty (%)
80
70
60
20
30
40
50
0.82
0.78
0.80
0.81
0.79
10
90
V
IN
+
R1
C1
FB
RT9203/A
V
OUT
L
R2
<1K
C
OUT
×
OUT
FB
R1
V
= V
(1+
)
R2
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| RT9203APS | Dual Regulators - Synchronous Buck PWM DC-DC and Linear Controller |
| RT9203GS | Dual Regulators - Synchronous Buck PWM DC-DC and Linear Controller |
| RT9203PS | Dual Regulators - Synchronous Buck PWM DC-DC and Linear Controller |
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相關(guān)代理商/技術(shù)參數(shù) |
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|---|---|
| RT9203APS | 制造商:RICHTEK 制造商全稱:Richtek Technology Corporation 功能描述:Dual Regulators - Synchronous Buck PWM DC-DC and Linear Controller |
| RT9203GS | 制造商:RICHTEK 制造商全稱:Richtek Technology Corporation 功能描述:Dual Regulators - Synchronous Buck PWM DC-DC and Linear Controller |
| RT9203PS | 制造商:Richtek 功能描述:DC/DC (IC) |
| RT9204 | 制造商:RICHTEK 制造商全稱:Richtek Technology Corporation 功能描述:Dual Regulators - Standard Buck PWM DC-DC and Linear Controller |
| RT9204_07 | 制造商:RICHTEK 制造商全稱:Richtek Technology Corporation 功能描述:Dual Regulators - Standard Buck PWM DC-DC and Linear Controller |
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