Richtek RT8241 Manual

High efficiency single synchronous buck pwm controller

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High Efficiency Single Synchronous Buck PWM Controller
General Description
The RT8241 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 RT8241 supports on chip voltage programming function
between 0.675V and 0.9V by controlling GX 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 RT8241 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 RT8241 is intended for CPU core,
chipset, DRAM, or other low voltage supplies as low as
0.675V.
The RT8241 is available in a WQFN-12L 2x2 package.
Ordering Information
RT8241
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)
Switching Frequency Operation
A : 300kHz
B : 400kHz
C : 500kHz
Note :
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.
©
Copyright
2014 Richtek Technology Corporation. All rights reserved.
DS8241-03 January 2014
®
Features
Applications
Pin Configurations
Meet Intel VCCSA Voltage Slew Rate
Built-in 1% Reference Voltage
2-Bit Programmable Output Voltage with Integrated
Transition Support
Quick Load-Step Response within 100ns
4700ppm/° ° ° ° ° C Programmable Current Limit by Low
Side R
Sensing
DS(ON)
4.5V to 26V Battery Input Range
Internal Ramp Current Limit Soft-Start Control
Drives Large Synchronous Rectifier FETs
Integrated Boost Switch
Over/Under Voltage Protection
Thermal Shutdown
Power Good Indicator
RoHS Compliant and Halogen Free
Notebook Computers
CPU/GPU Core Supply
Chipset/RAM Supply
Generic DC/DC Power Regulator
(TOP VIEW)
12
LGATE
1
PHASE
2
UGATE
3
WQFN-12L 2x2
is a registered trademark of Richtek Technology Corporation.
RT8241
11
10
9
PGOOD
GND
G1
8
13
G0
7
4
5
6
www.richtek.com
1

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Summary of Contents for Richtek RT8241

  • Page 1 Integrated Boost Switch a relatively constant switching frequency. Over/Under Voltage Protection Thermal Shutdown The RT8241 achieves high efficiency at a reduced cost Power Good Indicator by eliminating the current-sense resistor found in RoHS Compliant and Halogen Free traditional current-mode PWMs. Efficiency is further...
  • Page 2: Marking Information

    Chip Enable PHASE 11 CS LGATE 13 (Exposed Pad) * : Optional Table 1. VID Table 0.9V 0.8V 0.725V 0.675V Copyright © 2014 Richtek Technology Corporation. All rights reserved. is a registered trademark of Richtek Technology Corporation. www.richtek.com DS8241-03 January 2014...
  • Page 3: Function Block Diagram

    LGATE LG R DS(ON) Latch 0.45V PGOOD leakage 85% V Diode Voltage Thermal Emuation Programmer Shutdown 10µA OC threshold © Copyright 2014 Richtek Technology Corporation. All rights reserved. is a registered trademark of Richtek Technology Corporation. DS8241-03 January 2014 www.richtek.com...
  • Page 4: Absolute Maximum Ratings

    = 300kHz) On-Time, Pulse Width RT8241B = 0.9V (f = 400kHz) RT8241C = 0.9V (f = 500kHz) Minimum Off-Time Copyright © 2014 Richtek Technology Corporation. All rights reserved. is a registered trademark of Richtek Technology Corporation. www.richtek.com DS8241-03 January 2014...
  • Page 5 EN Threshold Logic-High V EN Threshold Voltage Logic-Low Voltage Programming (G0, G1) G0, G1 Input Logic-High Threshold Logic-Low Voltage Copyright © 2014 Richtek Technology Corporation. All rights reserved. is a registered trademark of Richtek Technology Corporation. DS8241-03 January 2014 www.richtek.com...
  • Page 6 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. Copyright © 2014 Richtek Technology Corporation. All rights reserved. is a registered trademark of Richtek Technology Corporation. www.richtek.com DS8241-03 January 2014...
  • Page 7: Typical Operating Characteristics

    = 0.9V = 20V, V = 5V, V = 0.9V 0.001 0.01 0.001 0.01 Output Current (A) Output Current (A) Copyright © 2014 Richtek Technology Corporation. All rights reserved. is a registered trademark of Richtek Technology Corporation. DS8241-03 January 2014 www.richtek.com...
  • Page 8 = 5V, = 0.8V to 0.9V (5V/Div) (5V/Div) UGATE UGATE (20V/Div) (20V/Div) LGATE LGATE (10V/Div) (10V/Div) Time (20μs/Div) Time (20μs/Div) © Copyright 2014 Richtek Technology Corporation. All rights reserved. is a registered trademark of Richtek Technology Corporation. www.richtek.com DS8241-03 January 2014...
  • Page 9 = 5V, = 0.9V, I = 0A to 6A LOAD OUT_ac (20mV/Div) LOAD (5A/Div) UGATE (20V/Div) LGATE (10V/Div) Time (100μs/Div) Copyright © 2014 Richtek Technology Corporation. All rights reserved. is a registered trademark of Richtek Technology Corporation. DS8241-03 January 2014 www.richtek.com...
  • Page 10: Application Information

    RT8241 Application Information The RT8241 is of a constant on-time PWM controller which Diode-Emulation Mode provides four DC feedback voltages by controlling the G0 RT8241 automatically reduces switching frequency at light- and G1 digital input. The constant on-time PWM control load conditions to maintain high efficiency.
  • Page 11 If the negative current become large enough to trigger NOCP, the low side MOSFET will be turned off to prevent Copyright © 2014 Richtek Technology Corporation. All rights reserved. is a registered trademark of Richtek Technology Corporation. DS8241-03 January 2014 www.richtek.com...
  • Page 12 Current Limit Setting (OCP) The RT8241 supports cycle-by-cycle negative over current The RT8241 has a cycle-by-cycle current limiting control. The current limit circuit employs a unique “valley” current limiting in CCM Mode only. The over current limit is set to be negative but is the same absolute value as the positive sensing algorithm.
  • Page 13 MOSFET Gate Driver (UGATE, LGATE) Power On Reset (POR) occurs when VCC rises above The high side driver is designed to drive high current, low 3.7V (typ.). After POR is triggered, the RT8241 will reset N-MOSFET(s). When configured as a floating DS(ON) the fault latch and prepare the PWM for operation.
  • Page 14 ≤ For recommended operating condition specifications of π × × ESR C the RT8241, the maximum junction temperature is 125°C Copyright © 2014 Richtek Technology Corporation. All rights reserved. is a registered trademark of Richtek Technology Corporation. www.richtek.com DS8241-03 January 2014...
  • Page 15 The maximum power dissipation at T = 25°C can instability. For best performance of the RT8241, the be calculated by the following formula : following guidelines should be strictly followed. = (125°C − 25°C) / (165°C/W) = 0.606W for Connect an RC low-pass filter from VCC, (1μF and 10Ω...
  • Page 16: Outline Dimension

    Richtek product. Information furnished by Richtek is believed to be accurate and reliable. However, no responsibility is assumed by Richtek or its subsidiaries for its use; nor for any infringements of patents or other rights of third parties which may result from its use.

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