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| 型号： | LTC3826IUH#PBF |
| 厂商： | Linear Technology |
| 文件页数： | 22/36页 |
| 文件大小： | 0K |
| 描述： | IC REG CTRLR BUCK PWM CM 32-QFN |
| 标准包装： | 73 |
| 系列： | PolyPhase® |
| PWM 型： | 电流模式 |
| 输出数： | 2 |
| 频率 - 最大： | 585kHz |
| 占空比： | 99.4% |
| 电源电压： | 4 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： | 32-WFQFN 裸露焊盘 |
| 包装： | 管件 |
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LTC3826
APPLICATIONS INFORMATION
Topside MOSFET Driver Supply (C B , D B )
External bootstrap capacitors C B connected to the
BOOST pins supply the gate drive voltages for the top-
side MOSFETs. Capacitor C B in the Functional Diagram
is charged though external diode D B from INTV CC when
the SW pin is low. When one of the topside MOSFETs is
to be turned on, the driver places the C B voltage across
the gate-source of the desired MOSFET. This enhances
the MOSFET and turns on the topside switch. The switch
node voltage, SW, rises to V IN and the BOOST pin follows.
With the topside MOSFET on, the boost voltage is above
the input supply: V BOOST = V IN + V INTVCC . The value of the
boost capacitor C B needs to be 100 times that of the total
input capacitance of the topside MOSFET(s). The reverse
breakdown of the external Schottky diode must be greater
than V IN(MAX) . When adjusting the gate drive level, the
?nal arbiter is the total input current for the regulator. If
a change is made and the input current decreases, then
the ef?ciency has improved. If there is no change in input
current, then there is no change in ef?ciency.
Fault Conditions: Current Limit and Current Foldback
The LTC3826 includes current foldback to help limit load
current when the output is shorted to ground. If the out-
put falls below 70% of its nominal output level, then the
maximum sense voltage is progressively lowered from
100mV to 30mV. Under short-circuit conditions with very
low duty cycles, the LTC3826 will begin cycle skipping in
order to limit the short-circuit current. In this situation the
bottom MOSFET will be dissipating most of the power but
less than in normal operation. The short-circuit ripple cur-
rent is determined by the minimum on-time t ON(MIN) of the
LTC3826 (≈230ns), the input voltage and inductor value:
Δ I L(SC) = t ON(MIN) (V IN /L)
The resulting short-circuit current is:
Fault Conditions: Overvoltage Protection (Crowbar)
The overvoltage crowbar is designed to blow a system
input fuse when the output voltage of the regulator rises
much higher than nominal levels. The crowbar causes huge
currents to ?ow, that blow the fuse to protect against a
shorted top MOSFET if the short occurs while the control-
ler is operating.
A comparator monitors the output for overvoltage con-
ditions. The comparator (OV) detects overvoltage faults
greater than 10% above the nominal output voltage. When
this condition is sensed, the top MOSFET is turned off and
the bottom MOSFET is turned on until the overvoltage
condition is cleared. The bottom MOSFET remains on
continuously for as long as the OV condition persists; if
V OUT returns to a safe level, normal operation automati-
cally resumes. A shorted top MOSFET will result in a high
current condition which will open the system fuse. The
switching regulator will regulate properly with a leaky
top MOSFET by altering the duty cycle to accommodate
the leakage.
Phase-Locked Loop and Frequency Synchronization
The LTC3826 has a phase-locked loop (PLL) comprised of
an internal voltage-controlled oscillator (VCO) and a phase
detector. This allows the turn-on of the top MOSFET of
controller 1 to be locked to the rising edge of an external
clock signal applied to the PLLIN/MODE pin. The turn-on
of controller 2’s top MOSFET is thus 180 degrees out of
phase with the external clock. The phase detector is an
edge sensitive digital type that provides zero degrees
phase shift between the external and internal oscillators.
This type of phase detector does not exhibit false lock to
harmonics of the external clock.
The output of the phase detector is a pair of comple-
mentary current sources that charge or discharge the
I SC =
30mV
R SENSE
–
1
2
I L(SC)
external ?lter network connected to the PLLLPF pin. The
relationship between the voltage on the PLLLPF pin and
operating frequency, when there is a clock signal applied
3826fc
22
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| LTC3827EG-1 | 制造商:Linear Technology 功能描述:DC DC Cntrlr Dual-OUT Sync Step Down 4V to 36V Input 28-Pin SSOP |
| LTC3827EG-1#PBF | 功能描述:IC REG CTRLR BUCK 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:PolyPhase® 标准包装:2,000 系列:- PWM 型:电流模式 输出数:1 频率 - 最大:1MHz 占空比:50% 电源电压:9 V ~ 10 V 降压:无 升压:是 回扫:是 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:8-TSSOP（0.173"，4.40mm 宽） 包装:带卷 (TR) |
| LTC3827EG-1#TRPBF | 功能描述:IC REG CTRLR BUCK 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:PolyPhase® 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 |
| LTC3827EUH#PBF | 功能描述:IC REG CTRLR BUCK 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:PolyPhase® 标准包装:2,000 系列:- PWM 型:电流模式 输出数:1 频率 - 最大:1MHz 占空比:50% 电源电压:9 V ~ 10 V 降压:无 升压:是 回扫:是 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:8-TSSOP（0.173"，4.40mm 宽） 包装:带卷 (TR) |
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