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參數(shù)資料
| 型號： | RT9204CS |
| 廠商： | Richtek Technology Corporation |
| 元件分類： | 線性穩(wěn)壓 |
| 英文描述： | Dual Regulator - Standard Buck PWM DC-DC and Linear Power Controller |
| 中文描述： | 雙穩(wěn)壓器-標準降壓PWM型DC - DC與線性電源控制器 |
| 文件頁數(shù)： | 3/14頁 |
| 文件大?。?/td> | 276K |
| 代理商： | RT9204CS |
Preliminary
RT9204
DS9204-00 February 2002
www.richtek-ic.com.tw
11
Reference Voltage
Because RT9204 use a low 35dB gain error amplifier,
shown in Fig. 8. The voltage regulation is dependent
on VIN & VOUT setting. The FB reference voltage of
0.8V were trimmed at VIN = 5V & VOUT = 2.5V
condition. In a fixed VIN = 5V application, the FB
reference voltage vs. VOUT voltage can be calculated
as Fig. 9.
Fig. 8
Fig. 9
Feedback Divider
The reference of RT9204 is 0.8V. Both the PWm and
LDO output voltages can be set using a resistor
based divider as shown in Fig.9. Put the R1&R2 and
R3&R4 as close as possible to FB pin and R2&R4
should be less than 1 k
to avoid noise coupling. 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
F is enough for
C1.
Fig. 10
PWM Layout Considerations
MOSFETs switch very fast and efficiently. 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 ocer-voltage stress
on devices. Careful component placement layout 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 low side
MOSFET or Schottky diode. Any inductance in the
switched current path generates a large voltage spike
during the switching interval. Careful component
selections, layout of the critical components, and use
shorter and wider PCB traces help in minimizing the
magnitude of voltage spikes.
There are two sets of critical components in a DC-DC
converter using the RT9204. 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.
+
_
+
_
EA
+
_
PWM
REP
0.8V
I3
56K
I2
1K
FB
RAMP
1.75V
FB
(
V
)
VOUT (V)
VIN = 5V
4
3.5
3
1
1.5
2
2.5
0.82
0.88
0.8
0.81
0.79
0.5
4.5
VIN
COUT
+
VOUT1
RT9204
FB
L
R1
R2
< 1K
C1
FBL
R3
R4
< 1K
+
VOUT2
)
4
R
3
R
1
(
V
8
.
0
V
)
2
R
1
R
1
(
V
8
.
0
V
2
OUT
1
OUT
+
×
=
+
×
=
DRV
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相關代理商/技術參數(shù) |
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|---|---|
| RT9204GS | 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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| RT9205/ACS | 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 |
| RT9205_07 | 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 |
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