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參數(shù)資料
| 型號(hào)： | RC5051 |
| 廠商： | Fairchild Semiconductor Corporation |
| 英文描述： | Programmable Synchronous DC-DC Controller for Low Voltage Microprocessors(用于低電壓微處理器的可編程同步DC-DC控制器) |
| 中文描述： | 可編程同步DC - DC控制器為低電壓微處理器（用于低電壓微處理器的可編程同步的DC - DC控制器） |
| 文件頁數(shù)： | 12/16頁 |
| 文件大?。?/td> | 141K |
| 代理商： | RC5051 |
RC5051
PRODUCT SPECIFICATION
12
REV. 1.0.4 4/2/01
Figure 4. Gate Bias Configuration
Inductor Selection
Choosing the value of the inductor is a tradeoff between
allowable ripple voltage and required transient response. The
system designer can choose any value within the allowed
minimum to maximum range in order to either minimize rip-
ple or maximize transient performance. The first order equa-
tion (close approximation) for minimum inductance is:
V
V
–
f
V
in
where:
V
in
= Input Power Supply
V
out
= Output Voltage
f = DC/DC converter switching frequency
ESR = Equivalent series resistance of all output capacitors in
parallel
V
ripple
= Maximum peak to peak output ripple voltage
budget.
The first order equation for maximum allowed inductance is:
V
V
–
where:
C
o
= The total output capacitance
I
pp
= Maximum to minimum load transient current
V
tb
= The output voltage tolerance budget allocated to load
transient
D
m
= Maximum duty cycle for the DC/DC converter
(usually 95%).
Some margin should be maintained away from both L
min
and L
max
. Adding margin by increasing L almost always
adds expense since all the variables are predetermined by
system performance except for C
o
, which must be increased
to increase L. Adding margin by decreasing L can either be
done by purchasing capacitors with lower ESR or by increas-
ing the DC/DC converter switching frequency. The RC5051
is capable of running at high switching frequencies and
provides significant cost savings for the newer CPU systems
that typically run at high supply current.
RC5051 Short Circuit Current Characteristics
The RC5051 short circuit current characteristic includes a
hysteresis function that prevents the DC-DC converter from
oscillating in the event of a short circuit. Figure 5 shows the
typical characteristic of the DC-DC converter circuit with a
6.8 m
sense resistor. The converter exhibits a normal load
regulation characteristic until the voltage across the resistor
exceeds the internal short circuit threshold of 120mV
(= 17.5A * 6.8m
). At this point, the internal comparator
trips and signals the controller to reduce the converter’s duty
cycle to approximately 20%. This causes a drastic reduction
in the output voltage as the load regulation collapses into the
short circuit control mode. With a 40m
output short, the
voltage is reduced to 15A * 40m
= 600mV. The output
voltage does not return to its nominal value until the output
current is reduced to a value within the safe operating range
for the DC-DC converter.
Output Voltage vs. Output Current
RSENSE = 6m
Figure 5. RC5051 Short Circuit Characteristic
Schottky Diode Selection
The application circuit of Figure 1 shows a Schottky diode,
D2, which is used as a free-wheeling diode to assure that the
body-diode in Q2 does not conduct when the upper
MOSFET is turning off and the lower MOSFET is turning
on. It is undesirable for this diode to conduct because its high
forward voltage drop and long reverse recovery time
degrades efficiency, and so the Schottky provides a shunt
path for the current. Since this time duration is very short,
the selection criterion for the diode is that the forward volt-
age of the Schottky at the output current should be less than
the forward voltage of the MOSFET’s body diode.
Output Filter Capacitors
The output bulk capacitors of a converter help determine its
output ripple voltage and its transient response. It has
already been seen in the section on selecting an inductor that
the ESR helps set the minimum inductance, and the capaci-
tance value helps set the maximum inductance. For most
converters, however, the number of capacitors required is
PWM/PFM
Control
65-5051-07
VO
+5V
+12V
D2
1
μ
F
Q1
Q2
L2
RS
47
D1
VCCQP
HIDRV
LODRV
GNDP
C
OUT
L
min
------------------------------
)
out
V
V
ripple
---ESR
×
×
=
L
max
2C
O
(
------------------------------------------------
)
D
V
tb
I
PP
×
=
1.0
0.5
0
1.5
2.0
2.5
3.0
3.5
0
5
10
15
20
25
6
Output Current (A)
O
相關(guān)PDF資料 |
PDF描述 |
|---|---|
| RC5051M | Current-Mode SMPS Controller |
| RC5054 | Programmable Synchronous DC-DC Converter Controller for Low Voltage Microprocessors |
| RC5054A | Programmable Synchronous DC-DC Converter Controller for Low Voltage Microprocessors |
| RC5054AM | |
| RC5057 | High Performance Programmable Synchronous DC-DC Controller for Low Voltage Microprocessors |
相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| RC5051B WAF | 制造商:Fairchild Semiconductor Corporation 功能描述: |
| RC5051M | 功能描述:DC/DC 開關(guān)控制器 DC-DC Converter Prog Sync RoHS:否 制造商:Texas Instruments 輸入電壓:6 V to 100 V 開關(guān)頻率: 輸出電壓:1.215 V to 80 V 輸出電流:3.5 A 輸出端數(shù)量:1 最大工作溫度:+ 125 C 安裝風(fēng)格: 封裝 / 箱體:CPAK |
| RC5051M_32 | 功能描述:開關(guān)變換器、穩(wěn)壓器與控制器 DC-DC Converter Prog Sync RoHS:否 制造商:Texas Instruments 輸出電壓:1.2 V to 10 V 輸出電流:300 mA 輸出功率: 輸入電壓:3 V to 17 V 開關(guān)頻率:1 MHz 工作溫度范圍: 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:WSON-8 封裝:Reel |
| RC5051MT | 功能描述:開關(guān)變換器、穩(wěn)壓器與控制器 Prog Sync DC-DC Low Voltage UPS RoHS:否 制造商:Texas Instruments 輸出電壓:1.2 V to 10 V 輸出電流:300 mA 輸出功率: 輸入電壓:3 V to 17 V 開關(guān)頻率:1 MHz 工作溫度范圍: 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:WSON-8 封裝:Reel |
| RC5051MT_32 | 功能描述:開關(guān)變換器、穩(wěn)壓器與控制器 Prog Sync DC-DC Low Voltage UPS RoHS:否 制造商:Texas Instruments 輸出電壓:1.2 V to 10 V 輸出電流:300 mA 輸出功率: 輸入電壓:3 V to 17 V 開關(guān)頻率:1 MHz 工作溫度范圍: 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:WSON-8 封裝:Reel |
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