参数资料
型号: ISL6326CRZ
厂商: Intersil
文件页数: 24/30页
文件大小: 0K
描述: IC REG CTRLR BUCK PWM VM 40-QFN
标准包装: 50
PWM 型: 电压模式
输出数: 1
频率 - 最大: 275kHz
占空比: 25%
电源电压: 4.75 V ~ 5.25 V
降压:
升压:
回扫:
反相:
倍增器:
除法器:
Cuk:
隔离:
工作温度: 0°C ~ 70°C
封装/外壳: 40-VFQFN 裸露焊盘
包装: 管件
ISL6326
where V IDROOP is the voltage at the IDROOP pin, R IDROOP
is the resistor between the IDROOP pin and GND, I LOAD is
current (see Equation 1); d is the duty cycle (V OUT /V IN ); and
L is the per-channel inductance.
? I M ? 2 I L(P-P) ( 1 – d ) 2
P LOW , 1 = r DS ( ON ) ? ------ ? ( 1 – d ) + -----------------------------------
the total output current of the converter, R ISEN is the sense
resistor connected to the ISEN+ pin, N is the active channel
number, and R X is the resistance of the current sense
? N ? 12
(EQ. 24)
element, either the DCR of the inductor or R SENSE
depending on the sensing method.
The resistor from the IDROOP pin to GND should be chosen
to ensure that the voltage at the IDROOP pin is less than 2V
under the maximum load current.
If the IDROOP pin is not used, tie it to GND.
General Design Guide
An additional term can be added to the lower-MOSFET loss
equation to account for additional loss accrued during the
dead time when inductor current is flowing through the
lower-MOSFET body diode. This term is dependent on the
diode forward voltage at I M , V D(ON) the switching frequency,
f S and the length of dead times, t d1 and t d2 , at the beginning
and the end of the lower-MOSFET conduction interval
respectively as shown in Equation 25:
I P-P ?
? I
P LOW , 2 = V D ( ON ) f S ? ------ + I ---------- ? t
? d1 + ? ? ------ – ---------- ? ? d2
I M P-P M
? N
This design guide is intended to provide a high-level
explanation of the steps necessary to create a multiphase
power converter. It is assumed that the reader is familiar with
2 N 2
t
(EQ. 25)
many of the basic skills and techniques referenced in the
following sections. In addition to this guide, Intersil provides
complete reference designs that include schematics, bills of
materials, and example board layouts for all common
microprocessor applications.
Power Stages
The first step in designing a multiphase converter is to
determine the number of phases. This determination
depends heavily on the cost analysis, which in turn depends
on system constraints that differ from one design to the next.
Principally, the designer will be concerned with whether
components can be mounted on both sides of the circuit
board; whether through-hole components are permitted; and
the total board space available for power-supply circuitry.
Generally speaking, the most economical solutions are
those in which each phase handles between 15A and 20A.
All surface-mount designs will tend toward the lower end of
this current range. If through-hole MOSFETs and inductors
can be used, higher per-phase currents are possible. In
cases where board space is the limiting constraint, current
can be pushed as high as 40A per phase, but these designs
require heat sinks and forced air to cool the MOSFETs,
inductors and heat-dissipating surfaces.
Thus the total maximum power dissipated in each lower
MOSFET is approximated by the summation of P LOW,1 and
P LOW,2 .
UPPER MOSFET POWER CALCULATION
In addition to r DS(ON) losses, a large portion of the
upper-MOSFET losses are due to currents conducted
across the input voltage (V IN ) during switching. Since a
substantially higher portion of the upper-MOSFET losses are
dependent on switching frequency, the power calculation is
more complex. Upper MOSFET losses can be divided into
separate components involving the upper-MOSFET
switching times the lower-MOSFET body-diode
reverse-recovery charge (Q rr ) and the upper MOSFET
r DS(ON) conduction loss.
When the upper MOSFET turns off, the lower MOSFET does
not conduct any portion of the inductor current until the
voltage at the phase node falls below ground. Once the
lower MOSFET begins conducting, the current in the upper
MOSFET falls to zero as the current in the lower MOSFET
ramps up to assume the full inductor current. In Equation 26,
the required time for this commutation is t 1 and the
approximated associated power loss is P UP,1 .
I P-P ? ?
I M
P UP , 1 ≈ V IN ? ------ + ---------- ? ? ---- 1 ? f S
MOSFETs
The choice of MOSFETs depends on the current each
? N 2 ? ? 2 ?
t
(EQ. 26)
MOSFET will be required to conduct; the switching
frequency; the capability of the MOSFETs to dissipate heat;
and the availability and nature of heat sinking and air flow.
At turn on, the upper MOSFET begins to conduct and this
transition occurs over a time t 2 . In Equation 27, the
approximate power loss is P UP,2 .
P UP , 2 ≈ V IN ? ------ – ---------- ? ? ---- 2 ? f S
LOWER MOSFET POWER CALCULATION
The calculation for heat dissipated in the lower MOSFET is
simple, since virtually all of the heat loss in the lower
? I M I P-P ? ? t ?
? N 2 ? ? 2 ?
(EQ. 27)
MOSFET is due to current conducted through the channel
resistance (r DS(ON) ). In Equation 24, I M is the maximum
continuous output current; I P-P is the peak-to-peak inductor
24
A third component involves the lower MOSFET’s
reverse-recovery charge (Q rr ). Since the inductor current
has fully commutated to the upper MOSFET before the
lower-MOSFET’s body diode can draw all of Q rr , it is
FN9262.1
May 5, 2008
相关PDF资料
PDF描述
EBM12DRMN-S273 CONN EDGECARD 24POS .156 WW
EBM12DRMD-S273 CONN EDGECARD 24POS .156 WW
ISL8126CRZ IC REG CTRLR BUCK PWM VM 32-QFN
GEM43DSES-S243 CONN EDGECARD 86POS .156 EYELET
UPJ1A682MHD6 CAP ALUM 6800UF 10V 20% RADIAL
相关代理商/技术参数
参数描述
ISL6326CRZ-T 功能描述:电流型 PWM 控制器 W/ANNEAL 4-PHS VR11 CNTRLR COM RoHS:否 制造商:Texas Instruments 开关频率:27 KHz 上升时间: 下降时间: 工作电源电压:6 V to 15 V 工作电源电流:1.5 mA 输出端数量:1 最大工作温度:+ 105 C 安装风格:SMD/SMT 封装 / 箱体:TSSOP-14
ISL6326CRZ-TR5453 制造商:Intersil Corporation 功能描述:STD. ISL6326CRZ-T W/GOLD BOND WIRE ONLY - Tape and Reel
ISL6326IRZ 功能描述:电流型 PWM 控制器 W/ANNEAL 4-PHS VR11 CNTRLR IND RoHS:否 制造商:Texas Instruments 开关频率:27 KHz 上升时间: 下降时间: 工作电源电压:6 V to 15 V 工作电源电流:1.5 mA 输出端数量:1 最大工作温度:+ 105 C 安装风格:SMD/SMT 封装 / 箱体:TSSOP-14
ISL6326IRZ-T 功能描述:电流型 PWM 控制器 W/ANNEAL 4-PHS VR11 CNTRLR IND RoHS:否 制造商:Texas Instruments 开关频率:27 KHz 上升时间: 下降时间: 工作电源电压:6 V to 15 V 工作电源电流:1.5 mA 输出端数量:1 最大工作温度:+ 105 C 安装风格:SMD/SMT 封装 / 箱体:TSSOP-14
ISL6327ACRZ 功能描述:IC REG CTRLR BUCK PWM 48-QFN RoHS:是 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 切换控制器 系列:- 产品培训模块:Lead (SnPb) Finish for COTS Obsolescence Mitigation Program 标准包装:2,500 系列:- PWM 型:电流模式 输出数:1 频率 - 最大:275kHz 占空比:50% 电源电压:18 V ~ 110 V 降压:无 升压:无 回扫:无 反相:无 倍增器:无 除法器:无 Cuk:无 隔离:是 工作温度:-40°C ~ 85°C 封装/外壳:8-SOIC(0.154",3.90mm 宽) 包装:带卷 (TR)