Document
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RT8240A/B/C
High Efficiency Single Synchronous Buck PWM Controller
General Description
Features
The RT8240A/B/C 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 RT8240A/B/C supports on chip voltage programming function between 1V and 1.05V by controlling G0 digital inputs.
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 RT8240A/B/C 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 RT8240A/B/C is intended for CPU core, chipset, DRAM, or other low voltage supplies as low as 1V. The RT8240A/B/C is available in a WQFN -12L 2x2 package.
Ordering Information
RT8240A/B/C
z Built-in 0.5% Reference Voltage z 1 Bit Programmable Output Voltage Between 1V
and 1.05V with Integrated Transition Support z Output Voltage Range from 1V to 3.6V z Quick Load-Step Response within 100ns z Support Pure MLCC Output Capacitor z 4700ppm/°C Programmable Current Limit by Low
Side RDS(ON) Sensing z 4.5V to 26V Battery Input Range z Internal Ramp Current Limit Soft-Start Control z Drives Large Synchronous Rectifier FETs z Integrated Boost Switch z Over/Under Voltage Protection z Thermal Shutdown z Power Good Indicator z RoHS Compliant and Halogen Free
Applications
z Notebook Computers z CPU/GPU Core Supply z Chipset/RAM Supply z Generic DC/DC Power Regulator
Pin Configurations
(TOP VIEW)
GND G0 CS
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 :
Switching Frequency Operation A : 300kHz B : 400kHz C : 500kHz
Richtek products are :
` RoHS compliant and compatible with the current require-
ments of IPC/JEDEC J-STD-020.
` Suitable for use in SnPb or Pb-free soldering processes.
12 11 10
LGATE 1
PHASE 2 UGATE 3
GND
13
9 PGOOD
8 EN 7 RGND
4 56
BOOT VCC
VOUT
WQFN-12L 2x2
Copyright ©2014 Richtek Technology Corporation. All rights reserved. DS8240A/B/C-04 January 2014
is a registered trademark of Richtek Technology Corporation.
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RT8240A/B/C
Marking Information
RT8240AGQW 45: Product Code
45W
YMDNN : Date Code
RT8240AZQW 45: Product Code
45W
YMDNN : Date Code
RT8240BGQW
29 : Product Code
29W
YMDNN : Date Code
RT8240BZQW
29 : Product Code
29W
YMDNN : Date Code
RT8240CGQW 43 : Product Code
43W
YMDNN : Date Code
RT8240CZQW 43 : Product Code
43W
YMDNN : Date Code
Typical Application Circuit
(1) Remote Sense
RT8240A/B/C
VCC
5 VCC
BOOT 4
Chip Enable
UGATE 3 9 PGOOD
PHASE 2
8 EN 11 G0
LGATE 1
12, 13 (Exposed Pad) GND 10 CS
VOUT 6 RGND 7
Remote (+) Remote (-)
VIN VOUT
Copyright ©2014 Richtek Technology Corporation. All rights reserved.
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is a registered trademark of Richtek Technology Corporation.
DS8240A/B/C-04 January 2014
(2) Local Sense
RT8240A/B/C
VCC
5 VCC
BOOT 4
9 PGOOD
Chip Enable
8 EN
11 G0
12, 13 (Exposed Pad) GND 10 CS
UGATE 3
PHASE 2 LGATE 1 VOUT 6 RGND 7
VID Table
G0 VOUT 0 1V 1 1.05V
RT8240A/B/C
VIN VOUT
Copyright ©2014 Richtek Technology Corporation. All rights reserved. DS8240A/B/C-04 January 2014
is a registered trademark of Richtek Technology Corporation.
www.richtek.com 3
RT8240A/B/C
Functional Pin Description
Pin No. 1
2
3 4
Pin Name LGATE
PHASE
UGATE BOOT
5 VCC
6 VOUT 7 RGND 8 EN 9 PGOOD
10 CS
11 G0
12, 13 (Exposed Pad)
GND
Pin Function
Gate Drive Output for Low Side External MOSFET.
External Inductor Connection Pin for PWM Converter. It behaves as the current sense comparator input for low side MOSFET RDS(ON) sensing and reference voltage for on time generation.
Gate Drive Output for the High Side External MOSFET.
Supply Input for High Side Driver. Connect a capacitor to the floating node (PHASE) pin. Control Voltage Input. Provides the power for the buck controller, the low side driver and the bootstrap circuit for high side driver. Bypass to GND with a 4.7μF ceramic capacitor.
Output Voltage Feedback Input. Connect VOUT to converter output node. Remote Voltage Sense Ground Pin.
PWM Enable Pin. Pull low to GND to disable the PWM.
Open Drain Power Good Indicator. High impedance indicates power is good.
Current Limit Threshold Setting Input. Connect a setting resistor to GND and the current limit threshold is equal to 1/8 of the voltage at this pin.
Input Pin for Programming the Output Voltage Betw.