Richtek RT8237CZQW, RT8237DZQW Schematic [ru]

®

RT8237C/D

High Efficiency Single Synchronous Buck PWM Controller

General Description

The RT8237C/D PWM controller provides high efficiency, excellent transient response, and high DC output accuracy needed for stepping down high voltage batteries to generate low voltage CPU core, I/O, and chipset RAM supplies in notebook computers.

The constant on-time PWM control scheme handles wide input/output voltage ratios with ease and provides 100ns “instant-on” response to load transients while maintaining a relatively constant switching frequency.

The RT8237C/Dachieves high efficiency at a reduced cost by eliminating the current sense resistor found in traditional current mode PWMs. Efficiency is further enhanced by its ability to drive very large synchronous rectifier MOSFETs and enter diode emulation mode at light load condition. The buck conversion allows this device to directly step down high voltage batteries at the highest possible efficiency. The pre-set frequency selections minimize design effort required for new designs. The RT8237C/D is intended for CPU core, chipset, DRAM, or other low voltage supplies as low as 0.7V. The RT8237C is available in a WDFN-10L 3x3 package, The RT8237D is available in a WQFN-12L 2x2 package.

Features

Wide Input Voltage Range : 4.5V to 26V

Output Voltage Range : 0.7V to 3.3V

Built-in 0.5% 0.7V Reference Voltage

Quick Load-Step Response within 100ns

4700ppm/°C Programmable Current Limit by Low

Side RDS(ON) Sensing

4 Selectable Frequency Setting

Soft-Start Control

Drives Large Synchronous-Rectifier FETs

Integrated Boot Switch

Built-in OVP/OCP/UVP

Thermal Shutdown

Power Good Indicator

RoHS Compliant and Halogen Free

Applications

Notebook Computers

CPU Core Supply

Chipset/RAM Supply as Low as 0.7V

Generic DC/DC Power Regulator

Pin Configurations

(TOP VIEW)

	Ordering Information		PGOOD 1			10	BOOT
			CS 2		GND	9	UGATE
	RT8237	(2)	EN 3			8	PHASE
			FB 4			7	VCC
		Pin 1 Orientation	RF 5		11	6	LGATE
		(2) : Quadrant 2, Follow EIA-481-D		WDFN-10L 3x3
		Package Type
				RT8237C
		QW : WDFN-10L 3x3 (W-Type)
				GND	NC	RF
		QW : WQFN-12L 2x2 (W-Type)
		Lead Plating System		12	11	10
		Z : ECO (Ecological Element with	LGATE	1			9	FB
		Halogen Free and Pb free)
			VCC	2	GND		8	EN
		C : WDFN-10L 3x3
			PHASE	3		13	7	CS
	Note :	D : WQFN-12L 2x2		4	5	6
				UGATE	BOOT	PGOOD
	 RoHS compliant and compatible with the current require-
	Richtek products are :
	ments of IPC/JEDEC J-STD-020.			WQFN-12L 2x2

 Suitable for use in SnPb or Pb-free soldering processes.	RT8237D
Copyright ©2014 Richtek Technology Corporation. All rights reserved.	is a registered trademark of Richtek Technology Corporation.

DS8237C/D-06 February 2014	www.richtek.com
	1

RT8237C/D

Marking Information

RT8237CZQW				RT8237DZQW
			Z3 : Product Code						72 : Product Code
	Z3 YM		YMDNN : Date Code		72W				W : Date Code
	DNN

Typical Application Circuit

	R1
VCC	0
	C1
		R5
	1µF
		100k
	16V
Chip Enable
	RRF	ROC_SET
	470k
		30k
	* : Optional

			CBOOT	VIN
RT8237C/D		RBOOT	0.1µF
			50V
VCC	BOOT	0		C2
				10µF x 3
		RUGATE		50V
	UGATE
PGOOD		0						VOUT
				LOUT
								1.05V
EN				0.45µH
	PHASE	RLGATE					C6
	LGATE			R2*				COUT
							10µF x 2
RF		0						330µF x 2
							16V
CS				C3*	RFB1	R3*		16V
					5.1k	C4*
							C5*
GND	FB
					RFB2
					10k

Functional Pin Description

Pin No.		Pin Name		Pin Function
RT8237C	RT8237D
1	6	PGOOD	Open Drain	Power Good Indicator. High impedance indicates
			power is good.
			Current Limit Threshold Setting Input. Connect a setting resistor to
2	7	CS	GND and the current limit threshold is equal to 1/8 of the voltage
			at this pin.
3	8	EN	PWM Enable. Pull low to GND to disable the PWM.
4	9	FB	VOUT Feedback Input. Connect FB to a resistor voltage divider
			from VOUT to GND to adjust the output from 0.7V to 3.3V
			Switching Frequency Selection. Connect a resistance to select
			switching frequency as shown in Electrical Characteristics.
5	10	RF	The switching frequency is detected and latched after startup. This
			pin also controls Diode emulation mode or forced CCM selection.
			Pull down to GND with resistor : Diode Emulation Mode.
			Connect to PGOOD with resistor : forced CCM after PGOOD
			becomes high.
6	1	LGATE	Gate Drive Output for Low Side External MOSFET.
			Control Voltage Input. This pin provides the power for the buck
7	2	VCC	controller, the low side driver and the bootstrap circuit for high side
			driver. Bypass to GND with a 1 F ceramic capacitor.
Copyright ©2014 Richtek Technology Corporation. All rights reserved.				is a registered trademark of Richtek Technology Corporation.

www.richtek.com	DS8237C/D-06 February 2014
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			RT8237C/D
Pin No.		Pin Name	Pin Function
RT8237C	RT8237D
			External Inductor Connection Pin for PWM Converter. It behaves
8	3	PHASE	as the current sense comparator input for low side MOSFET
			RDS(ON) sensing and reference voltage for on time generation.
9	4	UGATE	Gate Drive Output for High Side External MOSFET.
10	5	BOOT	Supply Input for High Side Driver. Connect through a capacitor to
			the floating node (PHASE) pin.
---	11	NC	No Internal Connection.
11	12, 13	GND	Ground. The exposed pad must be soldered to a large PCB and
(Exposed Pad)	(Exposed Pad)		connected to GND for maximum power dissipation.

Function Block Diagram

TRIG

VCC

RF

On-time

Compute

BOOT

PHASE

1-SHOT

R

-COMP

S

Q

PWM

UGATE

+

DRV

VREF

Min. tOFF

PHASE

+

OV

Latch

Q

TRIG

125%

S1

Q

1-SHOT

VREF

-

Latch

DRV

LGATE

FB

+

UV

70%

S1

Q

GND

-

VREF

DEM/FCCM

125% VREF

-

PGOOD

+

VCC

POR

SS

-

Timer

90% VREF

+

EN

Thermal

-

Shutdown

+

X(1/8)

10µA

+

-

X(-1/8)

CS

Copyright ©2014 Richtek Technology Corporation. All rights reserved.

is a registered trademark of Richtek Technology Corporation.

DS8237C/D-06 February 2014	www.richtek.com
	3

RT8237C/D

Absolute Maximum Ratings					(Note 1)
 VCC, FB, PGOOD, EN, CS, RF to GND				----------------------------------------------------------------------------					−0.3V to 6V
 BOOT to PHASE ----------------------------------------------------------------------------------------------------------									−0.3V to 6V
 PHASE to GND
DC -----------------------------------------------------------------------------------------------------------------------------									−0.3V to 32V
<20ns ------------------------------------------------------------------------------------------------------------------------									−8V to 38V
 UGATE to PHASE --------------------------------------------------------------------------------------------------------									−0.3V to 6V
DC -----------------------------------------------------------------------------------------------------------------------------									−0.3V to 6V
<20ns ------------------------------------------------------------------------------------------------------------------------									−5V to 7.5V
 LGATE to GND -------------------------------------------------------------------------------------------------------------									−0.3V to 6V
DC -----------------------------------------------------------------------------------------------------------------------------									−0.3V to 6V
<20ns ------------------------------------------------------------------------------------------------------------------------									−2.5V to 7.5V
 Power Dissipation, PD @ TA = 25°C
WDFN-10L 3x3 -------------------------------------------------------------------------------------------------------------									0.952W
WQFN-12L 2x2 ------------------------------------------------------------------------------------------------------------									0.606W
 Package Thermal Resistance (Note 2)
WDFN-10L 3x3, θJA -------------------------------------------------------------------------------------------------------									105°C/W
WDFN-10L 3x3, θJC -------------------------------------------------------------------------------------------------------									8.2°C/W
WQFN-12L 2x2, θJA -------------------------------------------------------------------------------------------------------									165°C/W
 Lead Temperature (Soldering, 10 sec.) -------------------------------------------------------------------------------									260°C
 Junction Temperature -----------------------------------------------------------------------------------------------------									150°C
 Storage Temperature Range --------------------------------------------------------------------------------------------									−65°C to 150°C
 ESD Susceptibility (Note 3)
HBM (Human Body Model) ----------------------------------------------------------------------------------------------									2kV
MM (Machine Model) -----------------------------------------------------------------------------------------------------									200V
Recommended Operating Conditions (Note 4)
 Input Voltage, VIN ----------------------------------------------------------------------------------------------------------									4.5V to 26V
 Control Voltage, VCC ------------------------------------------------------------------------------------------------------									4.5V to 5.5V
 Junction Temperature Range --------------------------------------------------------------------------------------------									−40°C to 125°C
 Ambient Temperature Range --------------------------------------------------------------------------------------------									−40°C to 85°C
Electrical Characteristics
(VCC = 5V, TA = 25°C, unless otherwise specified)
Parameter		Symbol			Test Conditions		Min	Typ	Max		Unit
Input Power Supply
VCC Quiescent Supply		IQ		FB	forced above the	regulation	--	500	1250		A
Current				point, VEN = 5V,
VCC Shutdown Current		ISHDN		VCC current, VEN = 0V			--	--	1		A
CS Shutdown Current				CS pull to GND			--	--	1		A
FB Error Comparator		VREF		DEM			0.7005	0.704	0.7075		V
Threshold				DEM, TA = 40 to 85 C		(Note 5)	0.697	0.704	0.711
FB Input Bias Current				VFB = 0.735V			1	0.01	1		A
Copyright ©2014 Richtek Technology Corporation. All rights reserved.						is a registered trademark of Richtek Technology Corporation.

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RT8237C/D

Parameter		Symbol	Test Conditions		Min	Typ	Max	Unit
VOUT Voltage Range					0.7	--	3.3	V
			RRF = 470k	(Note 6)	--	290	--
Switching Frequency		fSW	RRF = 200k	(Note 6)	--	340	--	kHz
			RRF = 100k	(Note 6)	--	380	--
			RRF = 39k	(Note 6)	--	430	--
Minimum Off-Time					250	400	550	ns
Current Sensing
CS Source Current		ICS			9	10	11	A
CS Source Current TC					--	4700	--	ppm/ C
Zero Crossing Threshold			DEM		10	--	5	mV
			GND PHASE, VCS = 2.4V		280	300	320
Current Limit Threshold		VLIMIT	GND PHASE, VCS = 1.6V		185	200	215	mV
			GND PHASE, VCS = 0.4V		40	50	60
Negative Current Limit			PHASE GND, VCS = 2.4V		--	300	--
					--	200	--	mV
Threshold			PHASE GND, VCS = 1.6V
			PHASE GND, VCS = 0.4V		--	50	--
Protection Function
Output UV Threshold			With respect to error		65	70	75	%
			comparator threshold
OVP Threshold			With respect to error		120	125	130	%
			comparator threshold
OV Fault Delay			FB forced above OV threshold		--	5	--	s
VCC Under Voltage Lockout			Falling edge,
		UVLO	hysteresis = 100mV, PWM		3.7	3.9	4.1	V
Threshold
			disabled below this level
VOUT Soft-Start			From EN = high to VOUT = 95%		--	1300	--	s
UV Blank Time			From EN signal going high		--	3	--	ms
Thermal Shutdown		TSD			--	150	--	C
Driver On Resistance
UGATE Drive Source		RUGATEsr	BOOT PHASE forced to 5V		--	1.8	3.6
UGATE Drive Sink		RUGATEsk	BOOT PHASE forced to 5V		--	1.2	2.4
LGATE Drive Source		RLGATEsr	LGATE, High State		--	1.8	3.6
LGATE Drive Sink		RLGATEsk	LGATE, Low State		--	0.8	1.6
Dead Time			LGATE Rising (VPHASE = 1.5V)		--	30	--	ns
			UGATE Rising		--	30	--
Internal Boost Charging Switch			VCC to BOOT, 10mA		--	--	80
On Resistance
EN Threshold
EN Input	Logic-High	VIH			1.8	--	--	V
Threshold Voltage	Logic-Low	VIL			--	--	0.5
Copyright ©2014 Richtek Technology Corporation. All rights reserved.				is a registered trademark of Richtek Technology Corporation.

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RT8237C/D

Parameter	Symbol	Test Conditions	Min	Typ	Max	Unit
Mode Decision
VRF Threshold for DEM			--	--	0.5	V
VRF Threshold for FCCM			1.8	--	--	V
PGOOD
Trip Threshold (falling,		Measured at FB, with respect to	87	90	93	%
leaving PGOOD)		reference, Hysteresis = 3%
Trip Threshold (rising,		Measured at FB, with respect to	120	125	130	%
leaving PGOOD)		reference, Hysteresis = 3%
Fault Propagation Delay		Falling Edge, FB forced below	--	2.5	--	s
		PGOOD trip threshold
Output Low Voltage		ISINK = 1mA	--	--	0.4	V
Leakage Current		High State, forced to 5V	--	--	1	A

Note 1. Stresses beyond those listed “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to absolute maximum rating conditions may affect device reliability.

Note 2. θJA is measured at TA = 25°C on a low effective thermal conductivity single-layer test board per JEDEC 51-3. θJC is measured at the exposed pad of the package.

Note 3. Devices are ESD sensitive. Handling precaution is recommended.

Note 4. The device is not guaranteed to function outside its operating conditions. Note 5. Guaranteed by design. Not production tested.

Note 6. Not production tested. Test condition is VIN = 8V, VOUT = 1.1V, IOUT = 10A using application circuit.

Copyright ©2014 Richtek Technology Corporation. All rights reserved.

is a registered trademark of Richtek Technology Corporation.

www.richtek.com	DS8237C/D-06 February 2014
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