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| 型号： | ISL8105BCBZ |
| 厂商： | Intersil |
| 文件页数： | 12/16页 |
| 文件大小： | 0K |
| 描述： | IC REG CTRLR BUCK PWM VM 8-SOIC |
| 标准包装： | 980 |
| PWM 型： | 电压模式 |
| 输出数： | 1 |
| 频率 - 最大： | 330kHz |
| 占空比： | 100% |
| 电源电压： | 6.5 V ~ 14.4 V |
| 降压： | 是 |
| 升压： | 无 |
| 回扫： | 无 |
| 反相： | 无 |
| 倍增器： | 无 |
| 除法器： | 无 |
| Cuk： | 无 |
| 隔离： | 无 |
| 工作温度： | 0°C ~ 70°C |
| 封装/外壳： | 8-SOIC（0.154"，3.90mm 宽） |
| 包装： | 管件 |
ISL8105B
G MOD ( f ) = ------------------------------ ? -----------------------------------------------------------------------------------------------------------
V OSC
1 + s ( f ) ? ( ESR + DCR ) ? C + s ( f ) ? L ? C
1 + s ( f ) ? R 2 ? C 1
s ( f ) ? R 1 ? ( C 1 + C 2 )
1 + s ( f ) ? ( R 1 + R 3 ) ? C 3
? ? C 1 ? C 2 ? ?
( 1 + s ( f ) ? R 3 ? C 3 ) ? ? 1 + s ( f ) ? R 2 ? ? --------------------- ? ?
F P1 = ---------------------------------------------
C 1 ? C 2
2 π ? R 2 ? C 1
2 π ? R 2 ? ---------------------
F P2 = -------------------------------
F Z2 = -------------------------------------------------
d MAX ? V IN 1 + s ( f ) ? ESR ? C
2
G FB ( f ) = ---------------------------------------------------- ?
-------------------------------------------------------------------------------------------------------------------------
? ? C 1 + C 2 ? ?
G CL ( f ) = G MOD ( f ) ? G FB ( f ) where , s ( f ) = 2 π ? f ? j
(EQ. 9)
COMPENSATION BREAK FREQUENCY EQUATIONS
1 1
F Z1 = -------------------------------
C 1 + C 2
1 1
2 π ? ( R 1 + R 3 ) ? C 3 2 π ? R 3 ? C 3
(EQ. 10)
Figure 10 shows an asymptotic plot of the Buck converter’s
gain vs. frequency. The actual modulator gain has a high gain
peak dependent on the quality factor (Q) of the output filter,
which is not shown. Using the above guidelines should yield a
compensation gain similar to the curve plotted. The open loop
error amplifier gain bounds the compensation gain. Check the
compensation gain at F P2 against the capabilities of the error
amplifier. The closed loop gain, G CL , is constructed on the
log-log graph of Figure 10 by adding the modulator gain,
G MOD (in dB), to the feedback compensation gain, G FB (in
dB). This is equivalent to multiplying the modulator transfer
function and the compensation transfer function and then
plotting the resulting gain.
frequency. When designing compensation networks, select
target crossover frequencies in the range of 10% to 30% of
the switching frequency, f SW .
Component Selection Guidelines
Output Capacitor Selection
An output capacitor is required to filter the output and supply
the load transient current. The filtering requirements are a
function of the switching frequency and the ripple current.
The load transient requirements are a function of the slew
rate (di/dt) and the magnitude of the transient load current.
These requirements are generally met with a mix of
capacitors and careful layout.
For applications that have transient load rates above 1A/ns.
High frequency capacitors initially supply the transient and
slow the current load rate seen by the bulk capacitors. The
bulk filter capacitor values are generally determined by the
ESR (effective series resistance) and voltage rating
requirements rather than actual capacitance requirements.
High frequency decoupling capacitors should be placed as
close to the power pins of the load as physically possible. Be
careful not to add inductance in the circuit board wiring that
could cancel the usefulness of these low inductance
components. Consult with the manufacturer of the load on
specific decoupling requirements.
Use only specialized low-ESR capacitors intended for
switching-regulator applications for the bulk capacitors. The
bulk capacitor’s ESR will determine the output ripple voltage
and the initial voltage drop after a high slew-rate transient. An
aluminum electrolytic capacitor's ESR value is related to the
case size with lower ESR available in larger case sizes.
F Z 1 F Z2
F P1
MODULATOR GAIN
COMPENSATION GAIN
CLOSED LOOP GAIN
OPEN LOOP E/A GAIN
F P2
However, the equivalent series inductance (ESL) of these
capacitors increases with case size and can reduce the
usefulness of the capacitor to high slew-rate transient loading.
Unfortunately, ESL is not a specified parameter. Work with
your capacitor supplier and measure the capacitor’s
impedance with frequency to select a suitable component. In
20 log ? -------- ?
OSC
0
R2
? R1 ?
d MAX ? V IN
20 log ---------------------------------
V
G FB
most cases, multiple electrolytic capacitors of small case size
perform better than a single large case capacitor.
Output Inductor Selection
The output inductor is selected to meet the output voltage
LOG
F LC
F CE
F 0
G CL
G MOD
FREQUENCY
ripple requirements and minimize the converter ’s response
time to the load transient. The inductor value determines the
converter ’s ripple current and the ripple voltage is a function
of the ripple current. The ripple voltage and current are
FIGURE 10. ASYMPTOTIC BODE PLOT OF CONVERTER GAIN
approximated by Equation 11:
V IN - V OUT V OUT
A stable control loop has a gain crossing with close to a
-20dB/decade slope and a phase margin greater than +45°.
Δ I = -------------------------------- ? ----------------
F S x L V IN
Δ V OUT = Δ I x ESR
(EQ. 11)
Include worst case component variations when determining
phase margin. The mathematical model presented makes a
number of approximations and is generally not accurate at
frequencies approaching or exceeding half the switching
12
Increasing the value of inductance reduces the ripple current
and voltage. However, the large inductance values reduce
the converter ’s response time to a load transient.
FN6447.2
April 15, 2010
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相关代理商/技术参数 |
参数描述 |
|---|---|
| ISL8105BCBZ-T | 功能描述:IC REG CTRLR BUCK PWM VM 8-SOIC RoHS:是 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 切换控制器 系列:- 标准包装:4,500 系列:PowerWise® PWM 型:控制器 输出数:1 频率 - 最大:1MHz 占空比:95% 电源电压:2.8 V ~ 5.5 V 降压:是 升压:无 回扫:无 反相:无 倍增器:无 除法器:无 Cuk:无 隔离:无 工作温度:-40°C ~ 125°C 封装/外壳:6-WDFN 裸露焊盘 包装:带卷 (TR) 配用:LM1771EVAL-ND - BOARD EVALUATION LM1771 其它名称:LM1771SSDX |
| ISL8105BCRZ | 功能描述:IC REG CTRLR BUCK PWM VM 10-DFN 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) |
| ISL8105BCRZ-T | 功能描述:IC REG CTRLR BUCK PWM VM 10-DFN RoHS:是 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 切换控制器 系列:- 标准包装:4,500 系列:PowerWise® PWM 型:控制器 输出数:1 频率 - 最大:1MHz 占空比:95% 电源电压:2.8 V ~ 5.5 V 降压:是 升压:无 回扫:无 反相:无 倍增器:无 除法器:无 Cuk:无 隔离:无 工作温度:-40°C ~ 125°C 封装/外壳:6-WDFN 裸露焊盘 包装:带卷 (TR) 配用:LM1771EVAL-ND - BOARD EVALUATION LM1771 其它名称:LM1771SSDX |
| ISL8105BEVAL1Z | 功能描述:EVAL BOARD ISL8105B RoHS:是 类别:编程器，开发系统 >> 评估板 - DC/DC 与 AC/DC（离线）SMPS 系列:- 产品培训模块:Obsolescence Mitigation Program 标准包装:1 系列:True Shutdown™ 主要目的:DC/DC，步升 输出及类型:1，非隔离 功率 - 输出:- 输出电压:- 电流 - 输出:1A 输入电压:2.5 V ~ 5.5 V 稳压器拓扑结构:升压 频率 - 开关:3MHz 板类型:完全填充 已供物品:板 已用 IC / 零件:MAX8969 |
| ISL8105BEVAL2Z | 功能描述:EVALUATION BOARD FOR ISL8105B RoHS:是 类别:编程器，开发系统 >> 评估板 - DC/DC 与 AC/DC（离线）SMPS 系列:- 产品培训模块:Obsolescence Mitigation Program 标准包装:1 系列:True Shutdown™ 主要目的:DC/DC，步升 输出及类型:1，非隔离 功率 - 输出:- 输出电压:- 电流 - 输出:1A 输入电压:2.5 V ~ 5.5 V 稳压器拓扑结构:升压 频率 - 开关:3MHz 板类型:完全填充 已供物品:板 已用 IC / 零件:MAX8969 |
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