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參數(shù)資料
| 型號(hào)： | MAX8553 |
| 廠商： | Maxim Integrated Products, Inc. |
| 英文描述： | 4.5V to 28V Input. Synchronous PWM Buck Controllers for DDR Termination and Point-of-Load Applications |
| 中文描述： | 4.5V至28V輸入、同步PWM buck控制器，適合DDR端接和負(fù)載點(diǎn)應(yīng)用 |
| 文件頁數(shù)： | 16/24頁 |
| 文件大?。?/td> | 483K |
| 代理商： | MAX8553 |
This algorithm results in a nearly constant switching fre-
quency despite the lack of a fixed-frequency clock
generator. The actual switching frequency, which is
given by the following equation, varies slightly due to
the voltage drop across the on-resistance of the
MOSFETs and the DC resistance of the output inductor:
where D is the duty cycle:
where I
O
is the output current, R
DSONL
is the on-resis-
tance of the low-side MOSFET, R
DSONH
is the on-resis-
tance of the high-side MOSFET, and R
DC
is the DC
resistance of the output inductor. The ideal switching fre-
quency for V
REFIN
= 2.5V is about 550kHz. Switching fre-
quency increases for positive (sourcing) load current
and decreases for negative (sinking) load current, due to
the changing voltage drop across the low-side MOSFET,
which changes the inductor-current discharge ramp
rate. The on-times guaranteed in the
Electrical
Characteristics
are also influenced by switching delays
caused by the loading effect of the external power
MOSFETs.
The switching frequency can also be adjusted to a
value other than the preset frequencies by adding a
resistor voltage-divider at HSD. See the
Adjusting the
Switching Frequency
section.
VTTR Reference (MAX8553 Only)
The MAX8553
’
s VTTR output is capable of sourcing or
sinking up to 25mA of current. The VTTR output voltage
is one-half of the voltage applied to REFIN. Bypass
VTTR with at least a 1μF ceramic capacitor.
Voltage Reference
The voltage at REF is nominally 2.00V. Connect a 0.22μF
ceramic bypass capacitor between REF and GND.
EN and HSD (MAX8554 Only)
EN is a logic input used to enable or shut down the
MAX8554. Drive EN high or connect to V+ to enable the
output. Drive EN low to place the MAX8554 in low-
power shutdown mode, reducing input current to less
than 5μA (typ).
HSD senses the input voltage at the drain of the high-side
MOSFET, which is used to set the high-side MOSFET on-
time. For normal operation, connect HSD to the drain of
the high-side MOSFET.
EN/HSD Function (MAX8553 Only)
In order to reduce pin count and package size, the
MAX8553 features a dual-function input pin, EN/HSD.
When EN/HSD is pulled to ground, the internal circuitry
powers off, reducing current consumption to less than
5μA (typ). To enable normal operation, connect
EN/HSD to the drain of the high-side MOSFET through
a 5.1k
resistor (
Figure
2). In this configuration, EN/HSD
becomes an input that monitors the high-side MOSFET
drain voltage (converter input voltage) and uses that
measurement to calculate the appropriate on-time for the
converter. If the enable function is not used, connect
EN/HSD directly to the high-side MOSFET drain.
D
V
I
R
R
(
R
V
I
R
OUT
O
DSONL
DC
HSD
O
DSONL
DSONH
+
+
(
=
+
)
)
-
f
D
t
K
N
S
ON
×
=
1
M
4.5V to 28V Input, Synchronous PWM Buck Controllers
for DDR Termination and Point-of-Load Applications
16
______________________________________________________________________________________
Table
1. Configuration of FSEL (MAX8553)
FSEL CONNECTED TO
Ground
REF
Floating
VL
N
t
ON
(μs)
0.91
1.15
1.70
2.55
FREQUENCY (kHz)
550
400
300
200
CONDITION
V
OUT
/ V
EN/HSD
= 0.5
V
OUT
/ V
EN/HSD
= 0.5
V
OUT
/ V
EN/HSD
= 0.5
V
OUT
/ V
EN/HSD
= 0.5
1.07
1.33
2.00
3.00
Table
2. Configuration of FSEL (MAX8554)
FSEL CONNECTED TO
Ground
REF
Floating
VL
N
t
ON
(μs)
0.37
0.49
0.71
1.02
FREQUENCY (kHz)
550
400
300
200
CONDITION
1.07
1.33
2.00
3.00
V
HSD
= 12V, V
OUT
= 2.5V
V
HSD
= 12V, V
OUT
= 2.5V
V
HSD
= 12V, V
OUT
= 2.5V
V
HSD
= 12V, V
OUT
= 2.5V
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PDF描述 |
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| MAX8554 | 4.5V to 28V Input. Synchronous PWM Buck Controllers for DDR Termination and Point-of-Load Applications |
| MAX8554EEE | 4.5V to 28V Input, Synchronous PWM Buck Controllers for DDR Termination and Point-of-Load Applications |
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| MAX8553EEE | 4.5V to 28V Input, Synchronous PWM Buck Controllers for DDR Termination and Point-of-Load Applications |
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| MAX8553EEE | 功能描述:電流型 PWM 控制器 RoHS:否 制造商:Texas Instruments 開關(guān)頻率:27 KHz 上升時(shí)間: 下降時(shí)間: 工作電源電壓:6 V to 15 V 工作電源電流:1.5 mA 輸出端數(shù)量:1 最大工作溫度:+ 105 C 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:TSSOP-14 |
| MAX8553EEE+ | 功能描述:電流型 PWM 控制器 4.5-28V Input Synch Buck Controller RoHS:否 制造商:Texas Instruments 開關(guān)頻率:27 KHz 上升時(shí)間: 下降時(shí)間: 工作電源電壓:6 V to 15 V 工作電源電流:1.5 mA 輸出端數(shù)量:1 最大工作溫度:+ 105 C 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:TSSOP-14 |
| MAX8553EEE+T | 功能描述:電流型 PWM 控制器 4.5-28V Input Synch Buck Controller RoHS:否 制造商:Texas Instruments 開關(guān)頻率:27 KHz 上升時(shí)間: 下降時(shí)間: 工作電源電壓:6 V to 15 V 工作電源電流:1.5 mA 輸出端數(shù)量:1 最大工作溫度:+ 105 C 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:TSSOP-14 |
| MAX8553EEE-T | 功能描述:電流型 PWM 控制器 RoHS:否 制造商:Texas Instruments 開關(guān)頻率:27 KHz 上升時(shí)間: 下降時(shí)間: 工作電源電壓:6 V to 15 V 工作電源電流:1.5 mA 輸出端數(shù)量:1 最大工作溫度:+ 105 C 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:TSSOP-14 |
| MAX8554EEE | 功能描述:電流型 PWM 控制器 RoHS:否 制造商:Texas Instruments 開關(guān)頻率:27 KHz 上升時(shí)間: 下降時(shí)間: 工作電源電壓:6 V to 15 V 工作電源電流:1.5 mA 輸出端數(shù)量:1 最大工作溫度:+ 105 C 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:TSSOP-14 |
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