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参数资料
| 型号： | LTC1775IS#TR |
| 厂商： | Linear Technology |
| 文件页数： | 14/24页 |
| 文件大小： | 0K |
| 描述： | IC REG CTRLR BUCK PWM CM 16-SOIC |
| 标准包装： | 2,500 |
| PWM 型： | 电流模式 |
| 输出数： | 1 |
| 频率 - 最大： | 165kHz |
| 占空比： | 99% |
| 电源电压： | 4.3 V ~ 36 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 ~ 85°C |
| 封装/外壳： | 16-SOIC（0.154"，3.90mm 宽） |
| 包装： | 带卷 (TR) |
LTC1775
APPLICATIO S I FOR ATIO
EXTV CC Connection
The LTC1775 contains an internal P-channel MOSFET
switch connected between the EXTV CC and INTV CC pins.
Whenever the EXTV CC pin is above 4.7V the internal 5.2V
regulator shuts off, the switch closes and INTV CC power is
supplied via EXTV CC until EXTV CC drops below 4.5V. This
allows the MOSFET gate drive and control power to be
derived from the output or other external source during
normal operation. When the output is out of regulation
V PUMP ≈ 2(V OUT – V D ) < 7V
V IN
TK
TG
LTC1775
SW
EXTV CC
BG
+
V IN
C IN
BAT85
L1
+
1 μ F
0.22 μ F
VN2222LL
+
BAT85
BAT85
V OUT
C OUT
(start-up, short circuit) power is supplied from the internal
PGND
regulator. Do not apply greater than 7V to the EXTV CC pin
and ensure that EXTV CC ≤ V IN .
Significant efficiency gains can be realized by powering
Figure 5b: Capacitive Charge Pump for EXTV CC
1775 F05b
INTV CC from the output, since the V IN current supplying
the driver and control currents will be scaled by a factor of
Duty Cycle/Efficiency. For 5V regulators this simply means
connecting the EXTV CC pin directly to V OUT . However, for
3.3V and other lower voltage regulators, additional cir-
cuitry is required to derive INTV CC power from the output.
The following list summarizes the four possible connec-
tions for EXTV CC :
1. EXTV CC left open (or grounded). This will cause INTV CC
to be powered from the internal 5.2V regulator resulting
in a low current efficiency penalty of up to 10% at high
input voltages.
2. EXTV CC connected directly to V OUT . This is the normal
connection for a 5V regulator and provides the highest
efficiency.
3. EXTV CC connected to an output-derived boost network.
For 3.3V and other low voltage regulators, efficiency
gains can still be realized by connecting EXTV CC to an
output-derived voltage which has been boosted to
greater than 4.7V. This can be done with either an
inductive boost winding as shown in Figure 5a or a
capacitive charge pump as shown in Figure 5b.
4. EXTV CC connected to an external supply. If an external
supply is available in the 5V to 7V range (EXTV CC < V IN ),
it may be used to power EXTV CC .
Figure 6 shows how one can easily generate a suitable
EXTV CC voltage from V IN . This circuit still derives the gate
drive current from V IN , but it removes the power dissipa-
tion from the LTC1775 internal regulator and increases the
gate drive voltage.
V IN
V IN
TK
+
V IN
C IN
1N4148
V SEC
R1
D1
Q1
OPTIONAL
EXTV CC
CONNECTION
5V < V SEC < 7V
R4
LTC1775
EXTV CC
FCB
TG
SW
T1
1:N
? +
+
C SEC
1 μ F
V OUT
C OUT
6.8V EXTV CC
1775 F06
Figure 6. EXTV CC Power Supplied from V IN
R3
SGND
BG
PGND
1775 F05a
Note that R DS(ON) also varies with the gate drive level. If
gate drives other than the 5.2V INTV CC are used, this must
be accounted for when selecting the MOSFET R DS(ON) .
Particular care should be taken with applications where
Figure 5a: Secondary Output Loop and EXTV CC Connection
14
EXTV CC is connected to the output. When the output
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| LTC1778EGN | 功能描述:IC REG CTRLR BUCK PWM CM 16-SSOP RoHS:否 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 切换控制器 系列:- 标准包装:2,500 系列:- PWM 型:电流模式 输出数:1 频率 - 最大:500kHz 占空比:96% 电源电压:4 V ~ 36 V 降压:无 升压:是 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:24-WQFN 裸露焊盘 包装:带卷 (TR) |
| LTC1778EGN#PBF | 功能描述:IC REG CTRLR BUCK PWM CM 16-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:2,500 系列:- PWM 型:电流模式 输出数:1 频率 - 最大:500kHz 占空比:96% 电源电压:4 V ~ 36 V 降压:无 升压:是 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:24-WQFN 裸露焊盘 包装:带卷 (TR) |
| LTC1778EGN#TR | 功能描述:IC REG CTRLR BUCK PWM CM 16-SSOP RoHS:否 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 切换控制器 系列:- 标准包装:2,500 系列:- PWM 型:电流模式 输出数:1 频率 - 最大:500kHz 占空比:96% 电源电压:4 V ~ 36 V 降压:无 升压:是 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:24-WQFN 裸露焊盘 包装:带卷 (TR) |
| LTC1778EGN#TRPBF | 功能描述:IC REG CTRLR BUCK PWM CM 16-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:2,500 系列:- PWM 型:电流模式 输出数:1 频率 - 最大:500kHz 占空比:96% 电源电压:4 V ~ 36 V 降压:无 升压:是 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:24-WQFN 裸露焊盘 包装:带卷 (TR) |
| LTC1778EGN-1 | 功能描述:IC REG CTRLR BUCK PWM CM 16-SSOP RoHS:否 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 切换控制器 系列:- 标准包装:2,500 系列:- PWM 型:电流模式 输出数:1 频率 - 最大:500kHz 占空比:96% 电源电压:4 V ~ 36 V 降压:无 升压:是 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:24-WQFN 裸露焊盘 包装:带卷 (TR) |
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