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參數(shù)資料
| 型號： | LTC3827IG-1#TR |
| 廠商： | LINEAR TECHNOLOGY CORP |
| 元件分類： | 穩(wěn)壓器 |
| 英文描述： | 3 A DUAL SWITCHING CONTROLLER, 650 kHz SWITCHING FREQ-MAX, PDSO28 |
| 封裝： | 5.30 MM, PLASTIC, SSOP-28 |
| 文件頁數(shù)： | 4/32頁 |
| 文件大小： | 448K |
| 代理商： | LTC3827IG-1#TR |
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LTC3827-1
12
38271fe
OPERATION
Output Overvoltage Protection
An overvoltage comparator guards against transient over-
shoots as well as other more serious conditions that may
overvoltage the output. When the VFB pin rises more than
10% above its regulation point of 0.800V, the top MOSFET
is turned off and the bottom MOSFET is turned on until
the overvoltage condition is cleared.
Power Good (PGOOD1) Pin
The PGOOD1 pin is connected to an open drain of an internal
N-channel MOSFET. The MOSFET turns on and pulls the
PGOOD1 pin low when the VFB1 pin voltage is not within
±10% of the 0.8V reference voltage. The PGOOD1 pin is also
pulled low when the RUN1 pin is low (shut down). When
the VFB1 pin voltage is within the ±10% requirement, the
MOSFET is turned off and the pin is allowed to be pulled
up by an external resistor to a source of up to 8.5V.
THEORY AND BENEFITS OF 2-PHASE OPERATION
Why the need for 2-phase operation? Up until the
2-phase family, constant-frequency dual switching regula-
tors operated both channels in phase (i.e., single-phase
operation). This means that both switches turned on at
the same time, causing current pulses of up to twice the
amplitude of those for one regulator to be drawn from the
input capacitor and battery. These large amplitude current
pulses increased the total RMS current owing from the
input capacitor, requiring the use of more expensive input
capacitors and increasing both EMI and losses in the input
capacitor and battery.
With 2-phase operation, the two channels of the dual-
switching regulator are operated 180 degrees out of phase.
This effectively interleaves the current pulses drawn by the
switches, greatly reducing the overlap time where they add
together.
The result is a signicant reduction in total RMS
input current, which in turn allows less expensive input
capacitors to be used, reduces shielding requirements for
EMI and improves real world operating efciency.
Figure 1 compares the input waveforms for a representative
single-phase dual switching regulator to the LTC3827-1
2-phase dual switching regulator. An actual measure-
ment of the RMS input current under these conditions
shows that 2-phase operation dropped the input current
from 2.53ARMS to 1.55ARMS. While this is an impressive
reduction in itself, remember that the power losses are
proportional to IRMS2,meaningthattheactualpowerwasted
is reduced by a factor of 2.66. The reduced input ripple
voltage also means less power is lost in the input power
path, which could include batteries, switches, trace/con-
nector resistances and protection circuitry. Improvements
in both conducted and radiated EMI also directly accrue as
a result of the reduced RMS input current and voltage.
Of course, the improvement afforded by 2-phase opera-
tion is a function of the dual switching regulator’s relative
Figure 1. Input Waveforms Comparing Single-Phase (a) and 2-Phase (b) Operation for Dual Switching Regulators
Converting 12V to 5V and 3.3V at 3A Each. The Reduced Input Ripple with the 2-Phase Regulator Allows
Less Expensive Input Capacitors, Reduces Shielding Requirements for EMI and Improves Efciency
IIN(MEAS) = 2.53ARMS
IIN(MEAS) = 1.55ARMS
38271 F01b
38271 F01a
5V SWITCH
20V/DIV
3.3V SWITCH
20V/DIV
INPUT CURRENT
5A/DIV
INPUT VOLTAGE
500mV/DIV
(a)
(b)
(Refer to Functional Diagram)
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| LTC3827IUH#TRPBF | 功能描述:IC REG CTRLR BUCK PWM CM 32-QFN RoHS:是 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - DC DC 切換控制器 系列:PolyPhase® 標(biāo)準(zhǔn)包裝:4,500 系列:PowerWise® PWM 型:控制器 輸出數(shù):1 頻率 - 最大:1MHz 占空比:95% 電源電壓:2.8 V ~ 5.5 V 降壓:是 升壓:無 回掃:無 反相:無 倍增器:無 除法器:無 Cuk:無 隔離:無 工作溫度:-40°C ~ 125°C 封裝/外殼:6-WDFN 裸露焊盤 包裝:帶卷 (TR) 配用:LM1771EVAL-ND - BOARD EVALUATION LM1771 其它名稱:LM1771SSDX |
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