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參數(shù)資料
| 型號： | MAX1994ETM |
| 廠商： | MAXIM INTEGRATED PRODUCTS INC |
| 元件分類： | 穩(wěn)壓器 |
| 英文描述： | Dual Step-Down Controllers Plus Linear- Regulator Controller for Notebook Computers |
| 中文描述： | DUAL SWITCHING CONTROLLER, 1000 kHz SWITCHING FREQ-MAX, CQCC48 |
| 封裝： | 7 X 7 MM, 0.80 MM HEIGHT, THIN, QFN-48 |
| 文件頁數(shù)： | 29/49頁 |
| 文件大小： | 983K |
| 代理商： | MAX1994ETM |
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M
Dual Step-Down Controllers Plus Linear-
Regulator Controller for Notebook Computers
BUCK1 Differential Remote-Sense
Amplifier (FBS, GDS)
The MAX1816/MAX1994 include differential remote-
sense inputs to eliminate the effect of voltage drops
down the PC board traces and through the processor
’
s
power leads. The FBS and GDS inputs enable true differ-
ential remote sense of the load voltage. The two inputs
measure the voltage directly across the load to provide a
signal that is summed with the feedback signals that set
the voltage-positioned output. Connect the feedback
sense input (FBS) directly to the positive load terminal
and connect the ground sense input (GDS) directly to
the negative load terminal. Modern microprocessors now
include dedicated V
CC
and ground-sense pins to
facilitate the measurement of the chip
’
s supply voltage.
BUCK1 Voltage-Positioning and
Current-Sense Inputs (CS1+, CS1-)
The CS1+ and CS1- pins are differential inputs that
measure the voltage drop across the sense resistor of
BUCK1 for current-limiting, zero-crossing detection and
active voltage positioning (Figure 4). The current-limit
threshold is adjusted with an external resistive voltage-
divider at ILIM1. A 10μA (min) divider current is recom-
mended. The current-limit threshold adjustment range
is from 25mV to 250mV. In adjustable mode, the cur-
rent-limit threshold is precisely 1/10th of the voltage at
ILIM1. The default current limit is 50mV when ILIM1 is
connected to V
CC
. The logic threshold for switchover to
the default value is approximately V
CC
- 1V.The default
current limit accommodates the low voltage drop
expected across the sense resistor.
The current-limit circuit of BUCK1 employs a unique
“
valley
”
current-sensing algorithm (Figure 6). If the
magnitude of the current-sense voltage between CS1+
and CS1- is above the current-limit threshold, the PWM
is not allowed to initiate a new cycle. The actual peak
current is greater than the current-limit threshold by an
amount equal to the inductor ripple current. Therefore,
the exact current-limit characteristic and maximum load
capability are a function of the sense resistance, induc-
tor value, and battery voltage.
There is also a negative current limit that prevents
excessive reverse inductor currents when V
OUT1
is
sinking current in PWM mode.
The negative current-limit threshold is set to approxi-
mately 140% of the positive current limit and therefore
tracks the positive current limit when ILIM1 is adjusted.
The GAIN pin controls the voltage-positioning gain. The
slope of the output voltage as a function of load current
is set by measuring the output current with a sense
resistor (R
SENSE
) in series with the inductor. An ampli-
fied version of this signal is fed back into the loop to
decrease the output voltage. The required offset is
added through the OFS0
–
OFS2 inputs (see the
BUCK1
Output-Voltage Offset Control
section). The exact rela-
tionship for the output of BUCK1 can be described with
the following equation:
V
OUT1
= V
SET
- A
VPS
×
(V
CS1+
- V
CS1-
) + V
OS
×
SF
where V
SET
is the programmed output voltage (see
Tables 5 and 6), V
OS
is the offset voltage generated
from the selected OFS_ pin, SF is a scale factor (0.125)
for the offset voltage, and A
VPS
is the differential volt-
age-positioning gain set with the GAIN pin.
Since V
CS1+
- V
CS1-
= I
LOAD
×
R
SENSE
, substituting the
differential sense voltage yields:
V
OUT1
= V
SET
- A
VPS
×
I
LOAD
×
R
SENSE
+ V
OS
×
SF
The GAIN pin is a four-level logic input. When GAIN is
set to GND, REF, open, and V
CC
, the differential volt-
age gains are 0, 1.5, 2, and 4, respectively. Grounding
GAIN disables the voltage-positioning function but
does not disable the current limit.
BUCK2 Current-Sense Input (CS2)
BUCK2 uses the voltage at the CS2 pin to estimate the
inductor current and determine the zero crossing for
controlling pulse-skipping operation (Figure 5).
Connect CS2 to the current-sense resistor (Figure 1) for
the best possible current-limit accuracy. However, the
improved accuracy is achieved at the expense of the
additional power loss in the sense resistor. CS2 can be
connected to LX2 for lossless current sensing. In this
case, the trade-off is that the current limit becomes
dependent on the low-side MOSFET
’
s R
DS(ON)
with its
inherent inaccuracies and thermal drift.
I
I
LIMIT
I
LOAD
0
TIME
I
PEAK
Figure 6.
“
Valley
”
Current-Limit Threshold Point
______________________________________________________________________________________________________
29
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PDF描述 |
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| MAX199AEWI | Fixed-Point Digital Signal Processor 532-FCBGA |
| MAX199AMYI | Circular Connector; No. of Contacts:18; Series:MS27505; Body Material:Aluminum; Connecting Termination:Crimp; Connector Shell Size:15; Circular Contact Gender:Socket; Circular Shell Style:Box Mount Receptacle RoHS Compliant: No |
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| MAX1994ETM+ | 功能描述:DC/DC 開關(guān)控制器 Integrated Circuits (ICs) 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 |
| MAX1994ETM+T | 功能描述:DC/DC 開關(guān)控制器 Integrated Circuits (ICs) 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 |
| MAX1994ETM-T | 功能描述:DC/DC 開關(guān)控制器 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 |
| MAX1994EVKIT | 功能描述:DC/DC 開關(guān)控制器 Evaluation Kit for the MAX1816 MAX1980 MAX1994 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 |
| MAX1995EGI | 功能描述:顯示驅(qū)動器和控制器 RoHS:否 制造商:Panasonic Electronic Components 工作電源電壓:2.7 V to 5.5 V 最大工作溫度: 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:QFN-44 封裝:Reel |
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