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参数资料
| 型号： | LTC3634IUFD#PBF |
| 厂商： | LINEAR TECHNOLOGY CORP |
| 元件分类： | 稳压器 |
| 英文描述： | 5.5 A DUAL SWITCHING CONTROLLER, 4600 kHz SWITCHING FREQ-MAX, PQCC28 |
| 封装： | 4 X 5 MM, LEAD FREE, PLASTIC, MO-220, QFN-28 |
| 文件页数： | 9/28页 |
| 文件大小： | 359K |
| 代理商： | LTC3634IUFD#PBF |
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LTC3634
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3634f
Checking Transient Response
The regulator loop response can be checked by observing
the response of the system to a load step. The ITH pin not
only allows optimization of the control loop behavior but
also provides a DC-coupled and AC filtered closed loop
response test point. The DC step, rise time, and settling
behavior at this test point reflect the closed loop response.
Assuming a predominantly second order system, phase
margin and/or damping factor can be estimated using the
percentage of overshoot seen at this pin.
After choosing compensation values as discussed in the
previous section, the design should be tested to verify
stability. The component values may be modified slightly
to optimize transient response once the final PC layout is
done and the particular output capacitor type and value
have been determined. The output capacitors need to be
selected because their various types and values determine
the loop gain and phase. An output current pulse of 20%
to 100% of full load current having a rise time of ~1μs will
produce output voltage and ITH pin waveforms that will
give a sense of the overall loop stability without breaking
the feedback loop.
Switching regulators take several cycles to respond to a
step in load current. When a load step occurs, VOUT im-
mediatelyshiftsbyanamountequaltoΔILOADESR,where
ESR is the effective series resistance of COUT. ΔILOAD also
begins to charge or discharge COUT,generatingafeedback
error signal used by the regulator to return VOUT to its
steady-state value. During this recovery time, VOUT can
be monitored for overshoot or ringing that would indicate
a stability problem.
When observing the response of VOUT to a load step,
the initial output voltage step may not be within the
bandwidth of the feedback loop, so the standard second
order overshoot/ DC ratio cannot be used to determine
phase margin. The output voltage settling behavior is
related to the stability of the closed-loop system and will
demonstrate the actual overall supply performance. For
a detailed explanation of optimizing the compensation
components, including a review of control loop theory,
refer to Application Note 76.
applicaTions inForMaTion
In some applications, a more severe transient can be
caused by switching in loads with large (>10μF) input
capacitors. The discharged input capacitors are effec-
tively put in parallel with COUT, causing a rapid drop in
VOUT. No regulator can deliver enough current to prevent
this problem, if the switch connecting the load has low
resistance and is driven quickly. The solution is to limit
the turn-on speed of the load switch driver. A Hot Swap
controller is designed specifically for this purpose and
usually incorporates current limiting, short-circuit protec-
tion, and soft-starting.
INTVCC Regulator Bypass Capacitor
Aninternallowdropout(LDO)regulatorproducesthe3.3V
supply that powers the internal bias circuitry and drives
the gate of the internal MOSFET switches. The INTVCC pin
connects to the output of this regulator and must have a
minimum of 1μF ceramic bypass capacitance to ground.
This capacitor should have low impedance electrical
connections to the INTVCC and PGND pins to provide the
transient currents required by the LTC3634. This supply
is intended only to supply additional DC load currents as
desired and not intended to regulate large transient or AC
behavior, as this may impact LTC3634 operation.
Boost Capacitor
TheLTC3634usesabootstrapcircuittocreateavoltagerail
above the applied input voltage VIN. Specifically, a boost
capacitor, CBOOST, is charged to a voltage approximately
equal to INTVCC each time the bottom power MOSFET is
turned on. The charge on this capacitor is then used to
supply the required transient current during the remainder
of the switching cycle. When the top MOSFET is turned on,
the BOOST pin voltage will be equal to approximately VIN
+ 3.3V. For most applications, a 0.1μF ceramic capacitor
closely connected between the BOOST and SW pins will
provide adequate performance.
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相关代理商/技术参数 |
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| LTC3634MPFE#PBF | 制造商:Linear Technology 功能描述:IC CONV DDR DDR2 DDR3 28TSSOP 制造商:Linear Technology 功能描述:BUCK 15V 3A 500KHZ-4MHZ TS 制造商:Linear Technology 功能描述:BUCK, 15V, 3A, 500KHZ-4MHZ, TSSOP-28 制造商:Linear Technology 功能描述:DP-SWREG/Monolithic, 15V Dual 3A Monolithic Step Down Regulator for DDR Power |
| LTC3634MPFE#TRPBF | 制造商:Linear Technology 功能描述:IC REG 15V 3A STEP DOWN 28-TSSOP 制造商:Linear Technology 功能描述:DC-DC REGULATOR, BUCK, ADJ, TSSOP-28, Primary Input Voltage:15V, No. of Outputs:2, Output Current:3A, No. of Pins:28, Operating Temperature Min:-55C, Operating Temperature Max:150C, MSL:-, Package / Case:28-TSSOP , RoHS Compliant: Yes |
| LTC3634MPUFD#PBF | 制造商:Linear Technology 功能描述:IC CONV DDR DDR2 DDR3 28-QFN 制造商:Linear Technology 功能描述:BUCK 15V 3A 500KHZ-4MHZ QF |
| LTC3637EDHC#PBF | 制造商:Linear Technology 功能描述:IC REG BUCK SYNC ADJ 1A 16DFN |
| LTC3637EMSE#PBF | 制造商:Linear Technology 功能描述:IC REG BUCK SYNC ADJ 1A 16MSOP |
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