Richtek RT8228AGQW, RT8228AZQW Schematic [ru]
®
RT8228A
Single Synchronous Buck PWM Controller
General Description
The RT8228A 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 RT8228A 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 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 Audio Skipping Mode (ASM) setting maintains the switching frequency above 25kHz, which eliminates noise in audio applications. The RT8228A is intended for CPU core, chipset, DRAM, or other low voltage supplies as low as 0.5V. The RT8228A is available in a WQFN-12L 2x2 package.
Ordering Information
RT8228A
Package Type
QW : WQFN-12L 2x2 (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.
Features
zBuilt in 1% 0.5V Reference Voltage
zAdjustable 0.5V to 3.3V Output Range
zQuick Load Step Response within 100ns
z4700ppm/°C Programmable Current Limit by Low
Side RDS(ON) Sensing
z4.5V to 26V Battery Input Range
zResistor Programmable Frequency
zInternal Ramp Current Limit Soft-Start Control
zDrives Large Synchronous Rectifier FETs
zIntegrated Boost Switch
zOver/Under Voltage Protection
zThermal Shutdown
zPower Good Indicator
zRoHS Compliant and Halogen Free
Applications
zNotebook Computers
zCPU Core Supply
zChipset/RAM Supply as Low as 0.5V
zGeneric DC/DC Power Regulator
Pin Configurations
(TOP VIEW)
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GND |
TON |
CS |
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12 |
11 |
10 |
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LGATE |
1 |
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9 |
PGOOD |
PHASE |
2 |
GND |
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8 |
EN |
UGATE |
3 |
13 |
7 |
MODE |
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4 |
5 |
6 |
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BOOT |
VCC |
FB |
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WQFN-12L 2x2 |
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Copyright ©2014 Richtek Technology Corporation. All rights reserved. |
is a registered trademark of Richtek Technology Corporation. |
DS8228A-06 January 2014 |
www.richtek.com |
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RT8228A
Marking Information
RT8228AGQW |
CQ : Product Code |
RT8228AZQW |
CQ : Product Code |
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CQW |
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W : Date Code |
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CQW |
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W : Date Code |
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Typical Application Circuit
VIN
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4.5V to 26V |
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R |
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TON |
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C4 |
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RT8228A |
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R4 |
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10µF |
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11 |
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4 |
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TON |
BOOT |
0 |
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C3 |
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VDDP |
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VCC |
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R5 |
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V |
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3 |
0 |
0.1µF |
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OUT |
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UGATE |
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1V |
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C2 |
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Q1 |
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L1 |
* : Optional |
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R2 |
4.7µF |
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PHASE |
2 |
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100k |
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LGATE |
1 |
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Q2 |
R7* |
C5* |
C6* |
C1 |
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220µF |
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R8 |
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PGOOD |
9 |
PGOOD |
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C7* |
10k |
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10 |
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CS |
FB |
6 |
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R6 |
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7 |
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To 5V : DEM |
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R9 |
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MODE |
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To 2.5V : ASM |
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10k |
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Chip Enable |
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EN |
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To GND : FCCM |
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12, |
13 (Exposed Pad) |
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GND |
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Copyright ©2014 Richtek Technology Corporation. All rights reserved. |
is a registered trademark of Richtek Technology Corporation. |
www.richtek.com |
RT8228A-06 January 2014 |
2
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RT8228A |
Functional Pin Description |
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Pin No. |
Pin Name |
Pin Function |
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1 |
LGATE |
Gate Drive Output for Low Side External MOSFET. |
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External Inductor Connection Pin for PWM Converter. It behaves as the current |
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2 |
PHASE |
sense comparator input for Low Side MOSFET RDS(ON) sensing and reference |
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voltage for on time generation. |
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3 |
UGATE |
Gate Drive Output for High Side External MOSFET. |
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4 |
BOOT |
Supply Input for High Side Driver. Connect through a capacitor to the floating |
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node (PHASE) pin. |
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Control Voltage Input. Provides the power for the buck controller, the low side |
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5 |
VCC |
driver and the bootstrap circuit for high side driver. Bypass to GND with a 4.7μF |
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ceramic capacitor. |
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6 |
FB |
VOUT Feedback Input. Connect FB to a resistive voltage divider from VOUT to |
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GND to adjust the output from 0.5V to 3.3V |
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Pull Down to GND for Forced CCM Mode. |
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7 |
MODE |
Pull Up to 2.5V for Audio Skipping Mode (ASM). |
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Pull Up to 5V for Diode Emulation Mode (DEM). |
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8 |
EN |
PWM Chip Enable. Pull low to GND to disable the PWM. |
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9 |
PGOOD |
Open Drain Power Good Indicator. High impedance indicates power is good. |
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10 |
CS |
Current Limit Threshold Setting Input. Connect a setting resistor to GND and the |
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current limit threshold is equal to 1/10 of the voltage at this pin. |
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11 |
TON |
On-time Setting. Connect a resistor between this pin and VIN. |
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12, |
GND |
Ground. The exposed pad must be soldered to a large PCB and connected to |
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13 (Exposed Pad) |
GND for maximum power dissipation. |
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Function Block Diagram
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TRIG |
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TON |
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On-time |
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Compute |
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BOOT |
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PHASE |
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1-SHOT |
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R |
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-COMP |
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PSR |
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S |
Q |
PWM |
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UGATE |
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+ |
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DRV |
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0.5V VREF |
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Min. TOFF |
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PHASE |
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+ |
OV |
Latch |
Q |
TRIG |
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VCC |
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125% VREF |
S1 |
Q |
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1-SHOT |
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- |
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Latch |
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DRV |
LGATE |
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FB |
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UV |
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70% VREF |
S1 |
Q |
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GND |
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+ |
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DEM/FCCM/ASM |
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MODE |
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125% VREF |
- |
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PGOOD |
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+ |
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VCC |
POR |
SS |
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- |
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Timer |
90% VREF |
+ |
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EN |
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Thermal |
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+ |
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10µA |
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Shutdown |
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- |
X(-1/10) |
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CS |
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Copyright ©2014 Richtek Technology Corporation. All rights reserved. |
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is a registered trademark of Richtek Technology Corporation. |
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RT8228A-06 January 2014 |
www.richtek.com |
3
RT8228A
Absolute Maximum Ratings (Note 1)
z VCC to GND --------------------------------------------------------------------------------------------------------- |
–0.3V to 6V |
z FB, PGOOD, EN, CS, MODE to GND ------------------------------------------------------------------------ |
–0.3V to (VCC + 0.3V) |
z TONtoGND ---------------------------------------------------------------------------------------------------------- |
–0.3V to 32V |
z BOOT to PHASE --------------------------------------------------------------------------------------------------- |
–0.3V to 6.5V |
z PHASE to GND |
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DC ---------------------------------------------------------------------------------------------------------------------- |
−0.3V to 32V |
< 20ns ---------------------------------------------------------------------------------------------------------------- |
−8V to 38V |
z UGATE to PHASE |
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DC ---------------------------------------------------------------------------------------------------------------------- |
−0.3V to (VCC + 0.3V) |
< 20ns ---------------------------------------------------------------------------------------------------------------- |
−5V to 7.5V |
z LGATE to GND |
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DC ---------------------------------------------------------------------------------------------------------------------- |
−0.3V to (VCC + 0.3V) |
< 20ns ---------------------------------------------------------------------------------------------------------------- |
−2.5V to 7.5V |
z Power Dissipation, PD @ TA = 25°C |
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WQFN-12L 2x2 ----------------------------------------------------------------------------------------------------- |
0.606W |
z Package Thermal Resistance (Note 2) |
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WQFN-12L 2x2, θJA ------------------------------------------------------------------------------------------------ |
165°C/W |
z Lead Temperature (Soldering, 10 sec.) ------------------------------------------------------------------------ |
260°C |
z Junction Temperature ---------------------------------------------------------------------------------------------- |
150°C |
z Storage Temperature Range ------------------------------------------------------------------------------------- |
−65°C to 150°C |
z ESD Susceptibility (Note 3) |
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HBM (Human Body Mode) --------------------------------------------------------------------------------------- |
2kV |
MM (Machine Mode) ----------------------------------------------------------------------------------------------- |
200V |
Recommended Operating Conditions |
(Note 4) |
z Input Voltage, VIN --------------------------------------------------------------------------------------------------- |
4.5V to 26V |
z Control Voltage, VCC ----------------------------------------------------------------------------------------------- |
4.5V to 5.5V |
z Junction Temperature Range ------------------------------------------------------------------------------------- |
−40°C to 125°C |
z Ambient Temperature Range ------------------------------------------------------------------------------------- |
−40°C to 85°C |
Copyright ©2014 Richtek Technology Corporation. All rights reserved. |
is a registered trademark of Richtek Technology Corporation. |
www.richtek.com |
RT8228A-06 January 2014 |
4 |
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RT8228A
Electrical Characteristics
(VCC = 5V, VIN = 15V, VEN = 5V, VMODE = 5V, RTON = 500kΩ, TA = 25°C, unless otherwise specified)
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Parameter |
Symbol |
Test Conditions |
Min |
Typ |
Max |
Unit |
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PWM Controller |
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VCC Quiescent Supply Current |
IQ |
FB forced above the regulation |
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0.5 |
1.25 |
mA |
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point, VEN = 5V |
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VCC Shutdown Current |
ISHDN |
VCC Current, VEN = 0V |
-- |
-- |
1 |
μ |
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A |
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TON Operating Current |
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RTON = 500k |
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30 |
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μ |
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A |
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TON Shutdown Current |
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RTON = 500k |
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1 |
μA |
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CS Shutdown Current |
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CS pull to GND |
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-- |
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1 |
μA |
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FB Error Comparator |
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VCC = 4.5V to 5.5V, DEM |
495 |
500 |
505 |
mV |
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Threshold Voltage |
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FB Input Bias Current |
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VFB = 0.5V |
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−1 |
0.1 |
1 |
μA |
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Output Voltage Range |
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0.5 |
-- |
3.3 |
V |
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On-Time |
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VIN =15V, VPHASE = 1.25V, |
267 |
334 |
401 |
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VMODE = 0V |
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Minimum Off-Time |
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VMODE = 0V, FB = 0.45V |
250 |
400 |
550 |
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Current Sensing Threshold |
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CS Source Current |
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VCS = 0.5V to 2V |
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9 |
10 |
11 |
μA |
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CS Source Current TC |
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On the basis of 25°C |
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4700 |
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ppm/°C |
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Zero Crossing Threshold |
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VMODE > 1.8V, PHASE − GND |
−10 |
-- |
5 |
mV |
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ASM Min Frequency |
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VMODE = 2.5V |
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-- |
25 |
-- |
kHz |
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Protection Function |
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Current Limit Threshold |
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GND − PHASE, VCS = 1V |
85 |
100 |
115 |
mV |
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UV Threshold |
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UVP Detect, FB Falling Edge |
60 |
70 |
80 |
% |
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OVP Threshold |
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OVP Detect, FB Rising Edge |
120 |
125 |
130 |
% |
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OV Fault Delay |
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FB forced above OV threshold |
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5 |
-- |
μs |
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VCC Power On Reset (POR) |
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Rising Edge |
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3.7 |
3.9 |
4.2 |
V |
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Threshold |
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POR Threshold Hysteresis |
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-- |
100 |
-- |
mV |
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Current Limit Ramp at |
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Enable to current limit threshold = |
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900 |
-- |
μs |
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Soft-Start |
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50mV |
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UV Blank Time |
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From EN signal going high |
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4.5 |
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ms |
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Thermal Shutdown |
TSD |
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-- |
150 |
-- |
°C |
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Thermal Shutdown Hysteresis |
TSD |
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-- |
10 |
-- |
°C |
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Driver On-Resistance |
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UGATE Driver Source |
RUGATEsr |
BOOT − PHASE forced to 5V, |
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2.5 |
5 |
Ω |
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UGATE High State |
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UGATE Driver Sink |
RUGATEsk |
BOOT − PHASE forced to 5V, |
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1.5 |
3 |
Ω |
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UGATE Low State |
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LGATE Driver Source |
RLGATEsr |
LGATE High State |
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-- |
2.5 |
5 |
Ω |
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LGATE Driver Sink |
RLGATEsk |
LGATE Low State |
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-- |
0.8 |
1.5 |
Ω |
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Dead Time |
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LGATE Rising (Phase = 1.5V) |
-- |
30 |
-- |
ns |
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UGATE Rising |
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-- |
30 |
-- |
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Copyright ©2014 Richtek Technology Corporation. All rights reserved. |
is a registered trademark of Richtek Technology Corporation. |
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RT8228A-06 January 2014 |
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www.richtek.com |
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5 |
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