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参数资料
| 型号： | LTC3788IGN-1#PBF |
| 厂商： | LINEAR TECHNOLOGY CORP |
| 元件分类： | 稳压器 |
| 英文描述： | DUAL SWITCHING CONTROLLER, 900 kHz SWITCHING FREQ-MAX, PDSO28 |
| 封装： | 0.150 INCH, LEAD FREE, PLASTIC, SSOP-28 |
| 文件页数： | 5/30页 |
| 文件大小： | 384K |
| 代理商： | LTC3788IGN-1#PBF |
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LTC3788-1
13
37881fb
operaTion
The typical capture range of the LTC3788-1’s PLL is from
approximately 55kHz to 1MHz, and is guaranteed to
lock to an external clock source whose frequency is be-
tween 75kHz and 850kHz.
The typical input clock thresholds on the PLLIN/MODE
pin are 1.6V (rising) and 1.2V (falling).
Operation When VIN > VOUT
When VIN rises above the regulated VOUT voltage, the
boost controller can behave differently depending on the
mode, inductor current and VIN voltage. In forced con-
tinuous mode, the loop works to keep the top MOSFET
on continuously once VIN rises above VOUT. The internal
charge pump delivers current to the boost capacitor to
maintain a sufficiently high TG voltage.
In pulse-skipping mode, if VINisbetween100%and110%
of the regulated VOUT voltage, TG turns on if the inductor
current rises above a certain threshold and turns off if the
inductor current falls below this threshold. This thresh-
old current is set approximately to 4% of the maximum
current. If the controller is programmed to Burst Mode
operation under this same VIN window, then TG remains
off regardless of the inductor current.
If VIN rises above 110% of the regulated VOUT voltage in
any mode, the controller turns on TG regardless of the
inductor current. In Burst Mode operation, however, the
internal charge pump turns off if the entire chip is asleep
(theotherchannelisasleeporshutdown).Withthecharge
pump off, there would be nothing to prevent the boost
capacitor from discharging, resulting in an insufficient TG
voltage needed to keep the top MOSFET completely on.
To prevent excessive power dissipation across the body
diode of the top MOSFET in this situation, the chip can be
switched over to forced continuous mode to enable the
charge pump, or a Schottky diode can also be placed in
parallel to the top MOSFET.
Power Good
The PGOOD1 pin is connected to an open-drain of an in-
ternal N-channel MOSFET. The MOSFET turns on and pulls
the PGOOD1 pin low when the corresponding VFB1 pin
voltage is not within ±10% of the 1.2V reference voltage.
ThePGOOD1pinisalsopulledlowwhenthecorresponding
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 6V.
Operation at Low SENSE Pin Common Voltage
The current comparator in the LTC3788-1 is powered
directly from the SENSE+ pin. This enables the common
mode voltage of SENSE+ and SENSE– pins to operate at as
low as 2.5V, which is below the UVLO threshold. Figure 1
shows a typical application when the controller’s VBIAS
is powered from VOUT while VIN supply can go as low as
2.5V. If the voltage on SENSE+ drops below 2.5V, the SS
pin will be held low. When the SENSE voltage returns to
the normal operating range, the SS pin will be released,
initiating a new soft-start cycle.
BOOST Supply Refresh and Internal Charge Pump
Each top MOSFET driver is biased from the floating
bootstrap capacitor CB, which normally recharges dur-
ing each cycle through an external diode when the bot-
tom MOSFET turns on. There are two considerations to
keep the BOOST supply at the required bias level. During
start-up, if the bottom MOSFET is not turned on within
100s after UVLO goes low, the bottom MOSFET will be
forced to turn on for ~400ns. This forced refresh gener-
ates enough BOOST-SW voltage to allow the top MOSFET
ready to be fully enhanced instead of waiting for the initial
few cycles to charge up. There is also an internal charge
pump that keeps the required bias on BOOST. The charge
pump always operates in both forced continuous mode
and pulse-skipping mode. In Burst Mode operation, the
charge pump is turned off during sleep and enabled when
the chip wakes up. The internal charge pump can normally
supply a charging current of 55A.
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相关代理商/技术参数 |
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| LTC3788IUH#TRPBF | 功能描述:IC REG CTRLR BST PWM CM 32-QFN 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 |
| LTC3789EGN#PBF | 功能描述:IC REG CTRLR BST PWM CM 28-SSOP 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 |
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