Datasheet > RT6551B

RT6551B

更新时间： 2024-02-15 05:26:54

品牌	Logo	应用领域
立锜 - RICHTEK		/
页数	文件大小	规格书
23页	284K
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技术参数
数据手册

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RT6551B 技术参数

Status：	Active	Vs (typ) (V)：	5
Vin (min) (V)：	4.5	Vin (max) (V)：	26
Vout (min) (V)：	0.675	Vout (max) (V)：	3.3
Preset Vout (V)：		Output Adj. Method：	Resistor
Accuracy (+/- %)：	1	Freq (typ) (kHz)：
Freq (min) (kHz)：		Freq (max) (kHz)：
Iq (typ) (mA)：	0.135	Features：	Adjustable Frequency;COT Control;Cycle-by-Cycle Current Limit;Diode Emulation Mode;Enable Input;Fast Transient Response;OVP;PSM;Power Good;Stable with Ceramic Capacitor;UVP
Package Type：	WQFN3x3-20

RT6551B 数据手册

RT6551A/B

Operation

Over-Voltage Protection (OVP) & Under-Voltage

Protection (UVP)

The RT6551A/B is a constant on-time synchronous step-

down controller. In normal operation, the high-side

N-MOSFET is turned on when the output voltage is lower

than VREF, and is turned off after the internal one-shot

timer expires. While the high-side N-MOSFET is turned

off, the low-side N-MOSFET is turned on to conduct the

inductor current until next cycle begins.

The output voltage is continuously monitored for over-

voltage and under-voltage protection. When the output

voltage exceeds its set voltage threshold( 115% of V_OUT),

UGATE goes low and LGATE is forced high. When the

feedback voltage is less than 0.45V, under-voltage

protection is triggered and then both UGATE and LGATE

gate drivers are forced low. The controller is latched until

VDDis re-supplied and exceeds the POR rising threshold

voltage or S5 is reset.

Soft-Start (SS)

For internal soft-start function, an internal current source

charges an internal capacitor to build the soft-start ramp

voltage. The output voltage will track the internal ramp

voltage during soft-start interval.

VTT Linear Regulator and VTTREF

This VTT linear regulator employs ultimate fast response

feedback loop so that small ceramic capacitors are enough

for keeping track of VTTREF within 40mV at all conditions,

including fast load transient. The VTTREF block consists

of on-chip 1/2 divider, LPF and buffer. This regulator also

has sink and source capability up to 10mA. Bypass

VTTREF toGNDwith a 33nF ceramic capacitor for stable

operation.

PGOOD

The power good output is an open-drain architecture. When

the soft-start is finished, the PGOOD open-drain output

will be high impedance.

Current Limit

The current limit circuit employs a unique “valley” current

sensing algorithm. If the magnitude of the current sense

signal at PHASE is above the current limit threshold, the

PWM is not allowed to initiate a new cycle. The current

limit threshold can be set with an external voltage setting

resistor on the CS pin.

is a registered trademark of Richtek Technology Corporation.

DS6551A/B-00 May 2015

www.richtek.com

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