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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： | 10/30页 |
| 文件大小： | 384K |
| 代理商： | LTC3788IGN-1#PBF |
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LTC3788-1
18
37881fb
applicaTions inForMaTion
Soft-Start (SS Pins)
The start-up of each VOUT is controlled by the voltage on
the respective SS pins. When the voltage on the SS pin
is less than the internal 1.2V reference, the LTC3788-1
regulates the VFB pin voltage to the voltage on the SS
pin instead of 1.2V.
Soft-startisenabledbysimplyconnectingacapacitorfrom
the SS pin to ground, as shown in Figure 5. An internal
10A current source charges the capacitor, providing a
linear ramping voltage at the SS pin. The LTC3788-1 will
regulate the VFB pin (and hence, VOUT) according to the
voltage on the SS pin, allowing VOUT to rise smoothly
from VIN to its final regulated value. The total soft-start
time will be approximately:
tSS = CSS
1.2V
10A
Figure 3. Normalized Output Capacitor Ripple
Current (RMS) for a Boost Converter
Figure 4. Setting Output Voltage
Figure 5. Using the SS Pin to Program Soft-Start
0.1
I ORIPPLE
/I
OUT
0.9
37881 F03
0.3
0.5
0.7 0.8
0.2
0.4
0.6
3.25
3.00
2.75
2.50
2.25
2.00
1.75
1.50
1.25
1.00
0.75
0.50
0.25
0
DUTY CYCLE OR (1-VIN/VOUT)
1-PHASE
2-PHASE
LTC3788-1
VFB
VOUT
RB
RA
37881 F04
LTC3788-1
SS
CSS
SGND
37881 F05
Multiple capacitors placed in parallel may be needed to
meet the ESR and RMS current handling requirements.
Dry tantalum, special polymer, aluminum electrolytic and
ceramic capacitors are all available in surface mount
packages. Ceramic capacitors have excellent low ESR
characteristics but can have a high voltage coefficient.
Capacitors are now available with low ESR and high ripple
current ratings (i.e., OS-CON and POSCAP).
Setting Output Voltage
The LTC3788-1 output voltages are each set by an exter-
nal feedback resistor divider carefully placed across the
output, as shown in Figure 4. The regulated output voltage
is determined by:
VOUT = 1.2V 1+
RB
RA
Great care should be taken to route the VFB line away from
noise sources, such as the inductor or the SW line.
INTVCC Regulators
The LTC3788-1 features two separate internal P-channel
low dropout linear regulators (LDO) that supply power at
the INTVCC pin from either the VBIAS supply pin or the
EXTVCC pin depending on the connection of the EXTVCC
pin. INTVCC powers the gate drivers and much of the
LTC3788-1’s internal circuitry. The VBIAS LDO and the
EXTVCC LDO regulate INTVCC to 5.4V. Each of these can
supply a peak current of 50mA and must be bypassed to
ground with a minimum of 4.7F ceramic capacitor. Good
bypassing is needed to supply the high transient currents
required by the MOSFET gate drivers and to prevent in-
teraction between the channels.
High input voltage applications in which large MOSFETs
are being driven at high frequencies may cause the maxi-
mum junction temperature rating for the LTC3788-1 to be
exceeded. The INTVCC current, which is dominated by the
gate charge current, may be supplied by either the VBIAS
LDO or the EXTVCC LDO. When the voltage on the EXTVCC
pin is less than 4.8V, the VBIAS LDO is enabled. In this
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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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