Document
RT8204L
Single Synchronous Buck Controller
General Description
The RT8204L 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 RT8204L achieves 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. The buck conversion allows this device to directly step down high voltage batteries for the highest possible efficiency. The RT8204L is intended for CPU core, chipset, DRAM, or other low voltage supplies as low as 0.75V. The RT8204L is available in a WQFN-16L 3x3 package. A built in LDO controller can drive an external N-MOSFET to provide a second output voltage from PWM output or other power source. The RT8204L can provide adjustable voltage down to 0.75V and maximum output voltage is dependen on the selected MOSFET. The internal 0.75V reference voltage with ±1.5% accuracy provides tight regulation of the output voltage. Other features such as independent enable control, open drain power good indicator, under voltage protection, and soft start make the RT8204L a system friendly power management solution for various applications.
Features
z
PWM Controller Ultra High Efficiency ` Resistor Programmable Current Limit by Low Side RDS(ON) Sense (Lossless Limit) ` 4700ppm/°C RDS(ON) Current Sensing ` Quick Load Step Response within 100ns ` 1% VFB Accuracy Over Line and Load ` Adjustable 0.75V to 3.3V Output Range ` 4.5V to 26V Battery Input Range ` Resistor Programmable Frequency ` Integrated Bootstrap Switch ` Over/Under Voltage Protection ` Voltage Ramp Soft-Start ` Power Good Indicator LDO Controller ` 1.5% accuracy Over Line and Load ` Independent Enable and Power Good Indicator ` Drive N-MOSFETs within Rail to Rail Controller Voltage ` MLCC and POSCAP Stable RoHS Compliant and Halogen Free
`
z
z
Applications
z z z
Notebook Computers CPU Core Supply Chipset/RAM Supply as Low as 0.75V
Ordering Information
RT8204L Package Type QW : WQFN-16L 3x3 (W-Type) Lead Plating System G : Green (Halogen Free and Pb Free) Z : ECO (Ecological Element with Halogen Free and Pb free)
Note : Richtek products are :
`
RoHS compliant and compatible with the current requirements of IPC/JEDEC J-STD-020. Suitable for use in SnPb or Pb-free soldering processes.
`
DS8204L-04 April 2011
www.richtek.com 1
RT8204L
Marking Information
RT8204LGQW J8= : Product Code YMDNN : Data Code
Pin Configurations
(TOP VIEW)
TON EN/DEM LEN BOOT
16 15 14 13
J8=YM DNN
VOUT VDD FB PGOOD
1 2 3 4 5 6
12
GND
17 7 8
11 10 9
UGATE PHASE OC VDDP
J8 : Product Code
J8 YM DNN
YMDNN : Data Code
WQFN-16L 3x3
Typical Application Circuit
VIN 4.5V to 26V RTON RT8204L TON C4 C3 Q1 L1 R6* C5* R7 C6* C8 VOUT1
16
VDDP 5V
BOOT 13
R4 R5
9 VDDP
C1 R1 R2
UGATE
12
2 VDD
C2
PHASE 11 LGATE 8 OC 10
RILIM
Q2
PGOOD CCM/DEM LDO Enable LDO PGOOD R3 VDDP
4 PGOOD 15 EN/DEM 14 LEN 5 LPGOOD
FB 3 R8 C7*
VOUT
1
C14 VOUT2 R11 C10 C9 R12 C11* C12 C13
LDRV
7
R9 R10
Q3
17 (Exposed Pad)
GND LFB
6
* : Optional
www.richtek.com 2
LPGOOD LFB LDRV LGATE
RT8204LZQW
DS8204L-04 April 2011
RT8204L
Function Block Diagram
VOUT TON SS (Internal)
TRIG On-time Compute 1-SHOT
+ + GM - +
Comp
R S Min. TOFF TRIG 1-SHOT DRV Diode Emulation Q DRV
BOOT UGATE PHASE
Q
+
OV
115% VREF FB 70% VREF
Latch S1 Q Latch S1 Q
-
VDDP LGATE PGND
+ -
UV
90% VREF VDD GND SS Ramp
+
Thermal Shutdown
20µA
+ -
OC
EN/DEM
PGOOD
LEN 0.75V VREF SS Ramp LFB 90% VREF
+ + -
SS X1 LDRV LPGOOD
50% VREF
+
LDO Controller
DS8204L-04 April 2011
www.richtek.com 3
RT8204L
Functional Pin Description
Pin No. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 Pin Name VOUT VDD FB PGOOD LPGOOD LFB LDRV LGATE VDDP OC PHASE UGATE BOOT LEN Pin Function Output Voltage Sense Pin. Connect this pin to the output of the PWM converter. VOUT is an input of the PWM controller. Analog Supply Voltage Input for Internal Analog Integrated Circuit. Bypass this pin to GND with a 1μF ceramic capacitor. Feedback Input of PWM Controller. Connect FB to a resistive voltage divider from VOUT to GND to adjust the output voltage from 0.75V to 3.3V. Power Good Signal Open-Drain Output of PWM Controller. This pin will be pulled high when the output voltage is within the target range. Power Good Signal Open-Drain Output of the LDO Regulator. This pin will be pulled high when the output voltage is within the target range. Feedback Input of LDO Regulator. This pin will be pulled high when the output voltage is within the target range. Drive Signal for LDO’s Path MOSFET. Low Side N-MOS.