8A, 23V Synchronous Step-Down Converter with 3.3V/5V LDO

RT6338

The RT6338 family are high efficiency synchronous step-down DC-DC converters with pseudo constant switching frequency 500kHz and deliver up to 8A output current. The RT6338A/B and RT6338AH/BH operate from 4.5V to 23V input voltage. The output voltage of RT6338A/AH is programmed between 0.6V to 5.5V and RT6338B/BH is fixed to 3.3V output voltage. The input voltage of RT6338C/CH ranges from 5.2V to 23V and the output voltage of RT6338C/CH is fixed to 5.1V.

The RT6338 adopts Advanced Constant On-Time (ACOT^®) control architecture that provides ultra-fast transient response and further reduces the external component count. In steady states, the ACOTV^® operates at nearly constant switching frequency over line, load and output voltage ranges and makes the EMI filter design easier.

By setting the voltage of the EN/MODE pin, RT6338 operates either in diode emulation mode (DEM) or ultrasonic mode (USM) at light load. The USM maintains operation frequency above 25kHz, which eliminates the acoustic noise. In the DEM, RT6338 provides the best light-load efficiency and improves the acoustic noise with spread spectrum function.

RT6338 provides PGOOD indicator for easy system sequence control. Full protection features are also integrated in the device, including the cycle-by-cycle current limit, OVP, UVP, input UVLO and OTP.

All above functions are integrated in a UQFN-23L 3x3 (FC) package.

Applications

Laptop Computers
Tablet PCs
Networking Systems
Servers
Personal Video Recorders
Flat Panel Television and Monitors
Distributed Power Systems

Key Spec.

	RT6338A	RT6338B	RT6338C
Status	Active	Active	Active
Vin (min) (V)	4.5	4.5	5.2
Vin (max) (V)	23	23	23
Number of Outputs	1	1	1
Vout (min) (V)	0.6	3.267	5.049
Vout (max) (V)	5.5	3.333	5.151
Output Adj. Method	Resistor	Fixed	Fixed
Iout (max) (A)	8	8	8
Current Limit (typ) (A)	10;12;14	12	12
Freq (typ) (kHz)	500	500	500
Ext Sync	No	No	No
Ron_HS (typ) (mOhm)	26	26	26
Ron_LS (typ) (mOhm)	14	14	14
Iq (typ) (mA)	0.085	0.095	0.095
Features	ACOT Control;Adjustable Current Limit;Cycle-by-Cycle Current Limit;Enable Input;Fast Transient Response;Internal Compensation;OCP;OTP;OVP;PSM;Power Good;Stable with Ceramic Capacitor;UVP	ACOT Control;Cycle-by-Cycle Current Limit;Enable Input;Fast Transient Response;Internal Compensation;OCP;OTP;OVP;PSM;Power Good;Stable with Ceramic Capacitor;UVP	ACOT Control;Cycle-by-Cycle Current Limit;Enable Input;Fast Transient Response;Internal Compensation;OCP;OTP;OVP;PSM;Power Good;Stable with Ceramic Capacitor;UVP
Package Type	UQFN3x3-23(FC)	UQFN3x3-23(FC)	UQFN3x3-23(FC)

Features

Input Voltage Range
► RT6338A/B and RT6338AH/BH : 4.5V to 23V
► RT6338C/CH : 5.2V to 23V
Output Voltage
► RT6338A/AH : 0.6V to 5.5V
► RT6338B/BH : 3.3V
► RT6338C/CH : 5.1V
8A Continuous Output Current
Stable with POSCAP and MLCC Capacitor
Fast Transient Response
Diode Emulation Mode (DEM) for Power Saving
Ultrasonic Mode (USM) for Avoiding Acoustic Noise
Pseudo Constant Switching Frequency 500kHz in CCM
Internal Power MOSFET Switch 26mΩ (high-side) and 14mΩ (low-side)
LDO
► RT6338B/BH : 3.3V/100mA
► RT6338C/CH : 5V/100mA
Over-Current Limit
► RT6338A/AH : Adjustable (10A, 12A or 14A)
► RT6338B/BH/C/CH : 12A
Output Under-/Over-Voltage Protection (UVP/OVP)
► RT6338A/B/C : Latched Mode UVP/OVP
► RT6338AH/BH/CH : Hiccup Mode UVP and Non-Latched Mode OVP
Input Under-Voltage Lockout (UVLO)
Over-Temperature Protection (OTP)
► RT6338A/B/C : Latched Mode OTP
► RT6338AH/BH/CH : Non-Latched Mode OTP