- 您現(xiàn)在的位置：買賣IC網(wǎng) > PDF目錄385522 > MAX1712 (Maxim Integrated Products, Inc.) High-Speed, Digitally Adjusted Step-Down Controllers for Notebook CPUs PDF資料下載
參數(shù)資料
| 型號： | MAX1712 |
| 廠商： | Maxim Integrated Products, Inc. |
| 英文描述： | High-Speed, Digitally Adjusted Step-Down Controllers for Notebook CPUs |
| 中文描述： | 高速、數(shù)字可調(diào)、降壓型控制器，用于筆記本電腦 |
| 文件頁數(shù)： | 14/28頁 |
| 文件大?。?/td> | 437K |
| 代理商： | MAX1712 |
第1頁第2頁第3頁第4頁第5頁第6頁第7頁第8頁第9頁第10頁第11頁第12頁第13頁當(dāng)前第14頁第15頁第16頁第17頁第18頁第19頁第20頁第21頁第22頁第23頁第24頁第25頁第26頁第27頁第28頁
M
High-Speed, Digitally Adjusted
Step-Down Controllers for Notebook CPUs
14
______________________________________________________________________________________
voltage rises approximately 1% (up to 1/2 the peak
amplitude of the ripple waveform as a limit) when under
light loads.
Integrators have both beneficial and detrimental char-
acteristics. While they do correct for drops due to DC
bus resistance and tighten the DC output voltage toler-
ance limits by averaging the peak-to-peak output
ripple, they can interfere with achieving the fastest pos-
sible load-transient response. The fastest transient
response is achieved when all three integrators are dis-
abled. This works very well when the MAX1710/
MAX1711/MAX1712 circuit can be placed very close to
the CPU.
There is often a connector, or at least many milliohms of
PC board trace resistance, between the DC-DC convert-
er and the CPU. In these cases, the best strategy is to
place most of the bulk bypass capacitors close to the
CPU, with just one capacitor on the other side of the con-
nector near the MAX1710/MAX1711/MAX1712 to control
ripple if the CPU card is unplugged. In this situation, the
remote-sense lines and integrators provide a real benefit.
When FBS is connected to V
so that all three integra-
tors are disabled, CC can be left unconnected, which
eliminates a component.
Automatic Pulse-Skipping Switchover
At light loads, an inherent automatic switchover to PFM
takes place. This switchover is effected by a comparator
that truncates the low-side switch on-time at the inductor
current’s zero crossing. This mechanism causes the
threshold between pulse-skipping PFM and nonskipping
PWM operation to coincide with the boundary between
continuous and discontinuous inductor-current operation
(also known as the “critical conduction” point;
see Continuous to Discontinuous Inductor Current Point
vs. Input Voltage graph in the
Typical Operating
Characteristics
). For a battery range of 7V to 24V, this
threshold is relatively constant, with only a minor depen-
dence on battery voltage.
where K is the On-Time Scale factor (Table 6). The load-
current level at which PFM/PWM crossover occurs,
I
LOAD(SKIP)
, is equal to 1/2 the peak-to-peak ripple cur-
rent, which is a function of the inductor value (Figure 3).
For example, in the standard application circuit with t
ON
= 300ns at 24V, V
OUT
= 2V, and L = 2μH, switchover to
pulse-skipping operation occurs at I
LOAD
= 1.65A or
about 1/4 full load. The crossover point occurs at an
even lower value if a swinging (soft-saturation) inductor
is used.
The switching waveforms may appear noisy and asyn-
chronous when light loading causes pulse-skipping
operation, but this is a normal operating condition that
results in high light-load efficiency. Trade-offs in PFM
noise vs. light-load efficiency can be made by varying
the inductor value. Generally, low inductor values pro-
duce a broader efficiency vs. load curve, while higher
values result in higher full-load efficiency (assuming that
the coil resistance remains fixed) and less output voltage
ripple. Penalties for using higher inductor values include
larger physical size and degraded load-transient
response (especially at low input voltage levels).
Forced-PWM Mode (
SKIP
= High)
The low-noise, forced-PWM mode (
SKIP
driven high) dis-
ables the zero-crossing comparator, which controls the
low-side switch on-time. This causes the low-side gate-
drive waveform to become the complement of the high-
side gate-drive waveform. This in turn causes the
inductor current to reverse at light loads, as the PWM
loop strives to maintain a duty ratio of V
OUT
/V
IN
. The
benefit of forced-PWM mode is to keep the switching fre-
quency fairly constant, but it comes at a cost: the no-
load battery current can be as high as 40mA or more.
Forced-PWM mode is most useful for reducing audio-fre-
quency noise, improving load-transient response, pro-
viding sink-current capability for dynamic output voltage
adjustment, and improving the cross-regulation of multi-
ple-output applications that use a flyback transformer or
coupled inductor.
Current-Limit Circuit (ILIM)
The current-limit circuit employs a unique “valley” cur-
rent-sensing algorithm that uses the on-state resistance
of the low-side MOSFET as a current-sensing element. If
the current-sense signal is above the current-limit
threshold, the PWM is not allowed to initiate a new cycle
(Figure 4). The actual peak current is greater than the
current-limit threshold by an amount equal to the induc-
I
K
L
LOAD SKIP
(
)
≈
2
Figure 3. Pulse-Skipping/Discontinuous Crossover Point
I
I
LOAD
= I
PEAK
/2
ON-TIME
0
TIME
-I
PEAK
L
V
BATT
- V
OUT
i
t
=
相關(guān)PDF資料 |
PDF描述 |
|---|---|
| MAX171 | 12 Bits ADC(光隔離，串行輸出,12位ADC) |
| MAX1720 | Switched Capacitor Voltage Inverter with Shutdown(帶關(guān)斷功能的開關(guān)電容電壓反相器) |
| MAX173 | Complete 5μs CMOS 12Bits ADC(CMOS，5μs,單通道，10位ADC) |
| MAX174 | 12 Bits ADC(工業(yè)標(biāo)準(zhǔn)，單通道，12位ADC) |
| MAX176 | Serial Output 12 Bits ADC(串行輸出，250ksps,串行，12位ADC) |
相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| MAX17120ETJ+ | 功能描述:LCD 驅(qū)動器 Triple Scan Driver for TFT LCD RoHS:否 制造商:Maxim Integrated 數(shù)位數(shù)量:4.5 片段數(shù)量:30 最大時鐘頻率:19 KHz 工作電源電壓:3 V to 3.6 V 最大工作溫度:+ 85 C 最小工作溫度:- 20 C 封裝 / 箱體:PDIP-40 封裝:Tube |
| MAX17120ETJ+T | 功能描述:LCD 驅(qū)動器 Triple Scan Driver for TFT LCD RoHS:否 制造商:Maxim Integrated 數(shù)位數(shù)量:4.5 片段數(shù)量:30 最大時鐘頻率:19 KHz 工作電源電壓:3 V to 3.6 V 最大工作溫度:+ 85 C 最小工作溫度:- 20 C 封裝 / 箱體:PDIP-40 封裝:Tube |
| MAX17120EVKIT+ | 功能描述:電源管理IC開發(fā)工具 MAX17120 Eval Kit RoHS:否 制造商:Maxim Integrated 產(chǎn)品:Evaluation Kits 類型:Battery Management 工具用于評估:MAX17710GB 輸入電壓: 輸出電壓:1.8 V |
| MAX17121ETG+ | 功能描述:LCD 驅(qū)動器 Dual Scan Driver for TFT LCD RoHS:否 制造商:Maxim Integrated 數(shù)位數(shù)量:4.5 片段數(shù)量:30 最大時鐘頻率:19 KHz 工作電源電壓:3 V to 3.6 V 最大工作溫度:+ 85 C 最小工作溫度:- 20 C 封裝 / 箱體:PDIP-40 封裝:Tube |
| MAX17121ETG+T | 功能描述:LCD 驅(qū)動器 Dual Scan Driver for TFT LCD RoHS:否 制造商:Maxim Integrated 數(shù)位數(shù)量:4.5 片段數(shù)量:30 最大時鐘頻率:19 KHz 工作電源電壓:3 V to 3.6 V 最大工作溫度:+ 85 C 最小工作溫度:- 20 C 封裝 / 箱體:PDIP-40 封裝:Tube |
發(fā)布緊急采購，3分鐘左右您將得到回復(fù)。