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参数资料
| 型号： | SP6655EB |
| 厂商： | Exar Corporation |
| 文件页数： | 9/17页 |
| 文件大小： | 0K |
| 描述： | EVAL BOARD FOR SP6655 |
| 标准包装： | 1 |
| 系列： | * |
S P 6 6 5 5
H i g h E f f i c i e n c y 4 0 0 m A S y n c h r o n o u s B u c k R e g u l a t o r
THEORY OF OPERATION
The SP6655 is a high efficiency synchronous
buck regulator with an input voltage range of
+2.7V to +5.5Vand an output that
is
adjustable between +1.0V and V IN . The
SP6655 features a unique on-time control loop
that runs in discontinuous conduction mode
(DCM) or continuous conduction mode (CCM)
using synchronous rectification. Other features
include over-temperature shutdown, over-
current protection, digitally controlled enable
and under-voltage lockout, a battery low
indicator, and an external feedback pin.
The SP6655 operates with a light load
quiescent current of 20μA using a 0.3Ω PMOS
main switch and a 0.3Ω NMOS synchronous
switch. It operates with excellent efficiency
across the entire load range, making it an
ideal solution for battery powered applications
and low current step-down conversions. The
part smoothly transitions into a 100% duty
cycle under heavy load/low input voltage
conditions.
O N -T IME C ONTROL - C HARGE P HASE
The SP6655 uses a precision comparator and a
minimum on-time to regulate the output
voltage and control the inductor current under
normal load conditions. As the feedback pin
drops below the regulation point, the loop
comparator output goes high and closes the
main switch. The minimum on-timer is
triggered, setting a logic high for the duration
defined by:
where:
K ON = 2.25V *μsec constant
V IN = V IN pin voltage
V OUT = V OUT pin voltage
To accommodate the use of ceramic and other
low ESR capacitors, an open loop ramp is
added to the feedback signal to mimic the
inductor current ripple. The following
waveforms describe the ideal ramp operation
in both CCM and DCM operation.
In either CCM or DCM, the negative going
ramp voltage (V RAMP in the functional diagram)
is added to FB and this creates the FB's signal.
This FB signal is applied to the negative
terminal of the loop comparator. The REF
voltage of 0.8V is applied to the positive
terminal of the loop comparator plus an offset
voltage V os to compensate for the DC level of
V RAMP applied to the negative terminal. The
result is an internal ramp with enough
negative going offset (approximately 50mV) to
trip the loop comparator whenever FB falls
below regulation.
The output of the loop comparator, a rising
VOLOW, causes a SET if BLANK = 0 and
OVR_I = 0. This starts inductor charging
(DRVON = 1) and starts the minimum on-
timer. The minimum on-timer times out and
indicates DRVON can be reset if the voltage
loop is satisfied. If V OUT is still below the
regulation point, RESET is held low until V OUT is
above regulation. Once RESET occurs, T ON
minimum is reset, and the T OFF one-shot is
triggered to blank the loop comparator from
starting a new charge cycle for a minimum
? 2012 Exar Corporation
9/17
Rev. 1.0.0
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相关代理商/技术参数 |
参数描述 |
|---|---|
| SP6655ER | 制造商:Rochester Electronics LLC 功能描述: 制造商:Exar Corporation 功能描述: |
| SP6655ER/TR | 制造商:SIPEX 制造商全称:Sipex Corporation 功能描述:High Efficiency 400mA Synchronous Buck Regulator Ideal for portable designs powered with Li Ion battery |
| SP6655ER-L | 功能描述:DC/DC 开关控制器 Regulator RoHS:否 制造商:Texas Instruments 输入电压:6 V to 100 V 开关频率: 输出电压:1.215 V to 80 V 输出电流:3.5 A 输出端数量:1 最大工作温度:+ 125 C 安装风格: 封装 / 箱体:CPAK |
| SP6655ER-L/TR | 功能描述:DC/DC 开关控制器 High Eff 400mA Synchronous RoHS:否 制造商:Texas Instruments 输入电压:6 V to 100 V 开关频率: 输出电压:1.215 V to 80 V 输出电流:3.5 A 输出端数量:1 最大工作温度:+ 125 C 安装风格: 封装 / 箱体:CPAK |
| SP6655EU-L | 功能描述:开关变换器、稳压器与控制器 High Eff 400mA Synchronous RoHS:否 制造商:Texas Instruments 输出电压:1.2 V to 10 V 输出电流:300 mA 输出功率: 输入电压:3 V to 17 V 开关频率:1 MHz 工作温度范围: 安装风格:SMD/SMT 封装 / 箱体:WSON-8 封装:Reel |
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