參數(shù)資料
型號(hào)： MAX1855
廠商： Maxim Integrated Products, Inc.
元件分類(lèi)： 數(shù)字信號(hào)處理
英文描述： Fixed-Point Digital Signal Processor 352-FC/CSP 0 to 0
中文描述： 高速、數(shù)字可調(diào)、同步降壓型控制器，集成電壓定位電路
文件頁(yè)數(shù)： 26/33頁(yè)
文件大?。?/td> 840K
代理商： MAX1855
M
High-Speed, Adjustable, Synchronous Step-Down
Controllers with Integrated Voltage Positioning
26
______________________________________________________________________________________
________________Applications Issues
Voltage Positioning and
Effective Efficiency
Powering new mobile processors requires careful
attention to detail to reduce cost, size, and power dissi-
pation. As CPUs became more power hungry, it was
recognized that even the fastest DC-DC converters
were inadequate to handle the transient power require-
ments. After a load transient, the output instantly
changes by ESR
COUT
×
I
LOAD
. Conventional DC-DC
converters respond by regulating the output voltage
back to its nominal state after the load transient occurs
(Figure 7). However, the CPU only requires that the out-
put voltage remain above a specified minimum value.
Dynamically positioning the output voltage to this lower
limit allows the use of fewer output capacitors and
reduces power consumption under load.
For a conventional (nonvoltage-positioned) circuit, the
total voltage change is:
V
P-P1
= 2
×
(ESR
COUT
×
I
LOAD
) + V
SAG
+ V
SOAR
where V
SAG
and V
SOAR
are defined in Figure 8. Setting
the converter to regulate at a lower voltage when under
load allows a larger voltage step when the output cur-
rent suddenly decreases (Figure 7). So the total voltage
change for a voltage positioned circuit is:
V
P-P2
= (ESR
COUT
×
I
LOAD
) + V
SAG
+ V
SOAR
where V
SAG
and V
SOAR
are defined in the
Design
Procedure.
Since the amplitudes are the same for both
circuits (V
P-P1
= V
P-P2
), the voltage-positioned circuit
requires only twice the ESR. Since the ESR specifica-
tion is achieved by paralleling several capacitors, fewer
units are needed for the voltage-positioned circuit.
An additional benefit of voltage positioning is reduced
power consumption at high load currents. Because the
output voltage is lower under load, the CPU draws less
current. The result is lower power dissipation in the
CPU, although some extra power is dissipated in
R
SENSE
. For a nominal 1.6V, 18A output (R
LOAD
=
89m
), reducing the output voltage 2.9% gives an out-
put voltage of 1.55V and an output current of 17.44A.
Given these values, CPU power consumption is
reduced from 28.8W to 27.03W. The additional power
consumption of R
SENSE
is:
2.5m
×
(17.44A)
2
= 0.76W
and the overall power savings is as follows:
28.8W - (27.03W + 0.76W) = 1.01W
In effect, 1.8W of CPU dissipation is saved and the
power supply dissipates much of the savings, but both
the net savings and the transfer of heat away from the
CPU are beneficial. Effective efficiency is defined as
the efficiency required of a nonvoltage-positioned cir-
cuit to equal the total dissipation of a voltage-posi-
tioned circuit for a given CPU operating condition.
Calculate effective efficiency as follows:
1) Start with the efficiency data for the positioned
circuit (V
IN
, I
IN
, V
OUT
, I
OUT
).
2) Model the load resistance for each data point:
I
LOAD
CAPACITOR SOAR
(ENERGY IN L
TRANSFERRED TO C
OUT
)
CAPACITIVE SAG
(dV/dt = I
OUT
/C
OUT
)
RECOVERY
ESR STEP-DOWN
AND STEP-UP
(I
STEP
X ESR)
V
OUT
Figure 8. Transient-Response Regions
B
1.6V
1.6V
A
A. CONVENTIONAL CONVERTER (50mV/div)
B. VOLTAGE POSITIONED OUTPUT (50mV/div)
VOLTAGE POSITIONING THE OUTPUT
MAX1716-Figure 07
Figure 7. Voltage Positioning the Output
相關(guān)PDF資料
PDF描述
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相關(guān)代理商/技術(shù)參數(shù)
參數(shù)描述
MAX1855EEG 功能描述:DC/DC 開(kāi)關(guān)控制器 RoHS:否 制造商:Texas Instruments 輸入電壓:6 V to 100 V 開(kāi)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
MAX1855EEG+ 制造商:Rochester Electronics LLC 功能描述: 制造商:Maxim Integrated Products 功能描述:
MAX1855EEG-T 功能描述:DC/DC 開(kāi)關(guān)控制器 RoHS:否 制造商:Texas Instruments 輸入電壓:6 V to 100 V 開(kāi)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
MAX1855EVKIT 功能描述:DC/DC 開(kāi)關(guān)控制器 Evaluation Kit for the MAX1716 MAX1854 MAX1855 RoHS:否 制造商:Texas Instruments 輸入電壓:6 V to 100 V 開(kāi)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
MAX1856EUB 功能描述:電信線路管理 IC RoHS:否 制造商:STMicroelectronics 產(chǎn)品:PHY 接口類(lèi)型:UART 電源電壓-最大:18 V 電源電壓-最小:8 V 電源電流:30 mA 最大工作溫度:+ 85 C 最小工作溫度:- 40 C 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:VFQFPN-48 封裝:Tray
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