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| 型号： | ISL8105BCBZ |
| 厂商： | Intersil |
| 文件页数： | 9/16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
a typical power supply to ramp up past 6.5V before the
soft-start ramps begins. This prevents a disturbance on the
output, due to the internal regulator turning on or off. If the
transition is slow (not a step change), the disturbance should
V OUT
be minimal. So while the recommendation is to not have the
output enabled during the transition through this region, it
may be acceptable. The user should monitor the output for
their application to see if there is any problem.
t0
2 SOFT-START CYCLES
t1
t2
The V IN to the top-side MOSFET can share the same supply
as V BIAS but can also run off a separate supply or other
sources, such as outputs of other regulators. If V BIAS
powers up first, and the V IN is not present by the time the
initialization is done, then the soft-start will not be able to
ramp the output, and the output will later follow part of the
FIGURE 5. OVERCURRENT RETRY OPERATION
Output Voltage Selection
The output voltage can be programmed to any level between
the 0.6V internal reference, up to the V Bias supply. The
ISL8105B can run at near 100% duty cycle at zero load, but
the r DS(ON) of the top-side MOSFET will effectively limit it to
something less as the load current increases. In addition, the
OCP (if enabled) will also limit the maximum effective duty
cycle.
An external resistor divider is used to scale the output
voltage relative to the internal reference voltage, and feed it
back to the inverting input of the error amp. See “Typical
upper resistor; R OFFSET (shortened to R 0 below) is the
lower one. The recommended value for R 1 is 1k Ω to 5k Ω
(±1% for accuracy) and then R OFFSET is chosen according
to the equation below. Since R 1 is part of the compensation
circuit (see “Feedback Compensation” on page 11), it is
often easier to change R OFFSET to change the output
voltage; that way the compensation calculations do not need
to be repeated. If V OUT = 0.6V, then R OFFSET can be left
open. Output voltages less than 0.6V are not available.
V IN ramp when it is applied. If this is not desired, then
change the sequencing of the supplies, or use the
COMP/EN pin to disable V OUT until both supplies are ready.
Figure 6 shows a simple sequencer for this situation. If V BIAS
powers up first, Q 1 will be off, and R 3 pulling to V BIAS will turn
Q 2 on, keeping the ISL8105B in shut-down. When V IN turns
on, the resistor divider R 1 and R 2 determines when Q 1 turns
on, which will turn off Q 2 and release the shut-down. If V IN
powers up first, Q 1 will be on, turning Q 2 off; so the ISL8105B
will start-up as soon as V BIAS comes up. The V DISABLE trip
point is 0.4V nominal, so a wide variety of NFET's or NPN's or
even some logic IC's can be used as Q 1 or Q 2 ; but Q 2 must be
low leakage when off (open-drain or open-collector) so as not to
interfere with the COMP output. Q 2 should also be placed near
the COMP/EN pin.
The V IN range can be as low as ~1V (for V OUT as low as the
0.6V reference). It can be as high as 20V (for V OUT just
below V IN ). There are some restrictions for running high V IN
voltage.
The first consideration for high V IN is the maximum BOOT
voltage of 36V. The V IN (as seen on LX) + V BIAS (boot
voltage - the diode drop) + any ringing (or other transients)
( R 1 + R 0 )
V OUT = 0.6V ? --------------------------
V OUT – 0.6V
R 0
R 1 ? 0.6V
R 0 = ----------------------------------
Input Voltage Considerations
The “Typical Application Diagram” on page 2 shows a
(EQ. 2)
(EQ. 3)
on the BOOT pin must be less than 36V. If V IN is 20V, that
limits V BIAS + ringing to 16V.
The second consideration for high V IN is the maximum (BOOT
- V BIAS ) voltage; this must be less than 24V. Since BOOT = V IN
+ V BIAS + ringing, that reduces to (V IN + ringing) must be <24V.
So based on typical circuits, a 20V maximum V IN is a good
starting assumption; the user should verify the ringing in their
particular application.
standard configuration where V BIAS is either 5V (±10%) or
12V (±20%); in each case, the gate drivers use the V BIAS
voltage for BGATE and BOOT/TGATE. In addition, V BIAS is
allowed to work anywhere from 6.5V up to the 14.4V
maximum. The V BIAS range between 5.5V and 6.5V is
NOT allowed for long-term reliability reasons, but
transitions through it to voltages above 6.5V are acceptable.
V IN
R 1
R 2
V BIAS
R 3
Q 1
TO COMP/EN
Q 2
There is an internal 5V regulator for bias; it turns on between
5.5V and 6.5V. Some of the delay after POR is there to allow
9
FIGURE 6. SEQUENCER CIRCUIT
FN6447.2
April 15, 2010
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| 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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