®
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 |
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10 |
BOOT |
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CS 2 |
GND |
9 |
UGATE |
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RT8237 |
(2) |
EN 3 |
8 |
PHASE |
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FB 4 |
7 |
VCC |
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Pin 1 Orientation |
RF 5 |
11 |
6 |
LGATE |
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(2) : Quadrant 2, Follow EIA-481-D |
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WDFN-10L 3x3 |
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Package Type |
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RT8237C |
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QW : WDFN-10L 3x3 (W-Type) |
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GND |
NC |
RF |
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QW : WQFN-12L 2x2 (W-Type) |
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Lead Plating System |
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12 |
11 |
10 |
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Z : ECO (Ecological Element with |
LGATE |
1 |
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9 |
FB |
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Halogen Free and Pb free) |
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VCC |
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GND |
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EN |
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C : WDFN-10L 3x3 |
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PHASE |
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13 |
7 |
CS |
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Note : |
D : WQFN-12L 2x2 |
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UGATE |
BOOT |
PGOOD |
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RoHS compliant and compatible with the current require- |
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Richtek products are : |
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ments of IPC/JEDEC J-STD-020. |
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WQFN-12L 2x2 |
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Suitable for use in SnPb or Pb-free soldering processes. |
RT8237D |
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Copyright ©2014 Richtek Technology Corporation. All rights reserved. |
is a registered trademark of Richtek Technology Corporation. |
DS8237C/D-06 February 2014 |
www.richtek.com |
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RT8237C/D
Marking Information
RT8237CZQW |
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RT8237DZQW |
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Z3 : Product Code |
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72 : Product Code |
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Z3 YM |
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YMDNN : Date Code |
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72W |
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W : Date Code |
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DNN |
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Typical Application Circuit
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R1 |
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VCC |
0 |
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C1 |
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R5 |
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1µF |
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100k |
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16V |
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Chip Enable |
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RRF |
ROC_SET |
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470k |
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30k |
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* : Optional |
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CBOOT |
VIN |
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RT8237C/D |
RBOOT |
0.1µF |
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50V |
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VCC |
BOOT |
0 |
C2 |
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10µF x 3 |
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RUGATE |
50V |
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UGATE |
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PGOOD |
0 |
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VOUT |
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LOUT |
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1.05V |
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EN |
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0.45µH |
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PHASE |
RLGATE |
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C6 |
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LGATE |
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R2* |
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COUT |
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10µF x 2 |
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RF |
0 |
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330µF x 2 |
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16V |
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CS |
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C3* |
RFB1 |
R3* |
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16V |
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5.1k |
C4* |
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C5* |
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GND |
FB |
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RFB2 |
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10k |
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Functional Pin Description
Pin No. |
Pin Name |
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Pin Function |
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RT8237C |
RT8237D |
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1 |
6 |
PGOOD |
Open Drain |
Power Good Indicator. High impedance indicates |
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power is good. |
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Current Limit Threshold Setting Input. Connect a setting resistor to |
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2 |
7 |
CS |
GND and the current limit threshold is equal to 1/8 of the voltage |
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at this pin. |
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3 |
8 |
EN |
PWM Enable. Pull low to GND to disable the PWM. |
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4 |
9 |
FB |
VOUT Feedback Input. Connect FB to a resistor voltage divider |
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from VOUT to GND to adjust the output from 0.7V to 3.3V |
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Switching Frequency Selection. Connect a resistance to select |
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switching frequency as shown in Electrical Characteristics. |
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5 |
10 |
RF |
The switching frequency is detected and latched after startup. This |
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pin also controls Diode emulation mode or forced CCM selection. |
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Pull down to GND with resistor : Diode Emulation Mode. |
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Connect to PGOOD with resistor : forced CCM after PGOOD |
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becomes high. |
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6 |
1 |
LGATE |
Gate Drive Output for Low Side External MOSFET. |
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Control Voltage Input. This pin provides the power for the buck |
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7 |
2 |
VCC |
controller, the low side driver and the bootstrap circuit for high side |
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driver. Bypass to GND with a 1 F ceramic capacitor. |
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Copyright ©2014 Richtek Technology Corporation. All rights reserved. |
is a registered trademark of Richtek Technology Corporation. |
www.richtek.com |
DS8237C/D-06 February 2014 |
2 |
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RT8237C/D |
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Pin No. |
Pin Name |
Pin Function |
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RT8237C |
RT8237D |
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External Inductor Connection Pin for PWM Converter. It behaves |
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8 |
3 |
PHASE |
as the current sense comparator input for low side MOSFET |
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RDS(ON) sensing and reference voltage for on time generation. |
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9 |
4 |
UGATE |
Gate Drive Output for High Side External MOSFET. |
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10 |
5 |
BOOT |
Supply Input for High Side Driver. Connect through a capacitor to |
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the floating node (PHASE) pin. |
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--- |
11 |
NC |
No Internal Connection. |
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11 |
12, 13 |
GND |
Ground. The exposed pad must be soldered to a large PCB and |
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(Exposed Pad) |
(Exposed Pad) |
connected to GND for maximum power dissipation. |
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Function Block Diagram
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TRIG |
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VCC |
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RF |
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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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S |
Q |
PWM |
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UGATE |
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+ |
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DRV |
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VREF |
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Min. tOFF |
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PHASE |
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+ |
OV |
Latch |
Q |
TRIG |
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125% |
S1 |
Q |
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1-SHOT |
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VREF |
- |
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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% |
S1 |
Q |
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GND |
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- |
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VREF |
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DEM/FCCM |
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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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Shutdown |
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+ |
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X(1/8) |
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10µA |
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+ |
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- |
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X(-1/8) |
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CS |
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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) |
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VCC, FB, PGOOD, EN, CS, RF to GND |
---------------------------------------------------------------------------- |
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−0.3V to 6V |
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BOOT to PHASE ---------------------------------------------------------------------------------------------------------- |
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−0.3V to 6V |
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PHASE to GND |
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DC ----------------------------------------------------------------------------------------------------------------------------- |
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−0.3V to 32V |
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<20ns ------------------------------------------------------------------------------------------------------------------------ |
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−8V to 38V |
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UGATE to PHASE -------------------------------------------------------------------------------------------------------- |
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−0.3V to 6V |
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DC ----------------------------------------------------------------------------------------------------------------------------- |
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−0.3V to 6V |
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<20ns ------------------------------------------------------------------------------------------------------------------------ |
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−5V to 7.5V |
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LGATE to GND ------------------------------------------------------------------------------------------------------------- |
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−0.3V to 6V |
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DC ----------------------------------------------------------------------------------------------------------------------------- |
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−0.3V to 6V |
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<20ns ------------------------------------------------------------------------------------------------------------------------ |
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−2.5V to 7.5V |
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Power Dissipation, PD @ TA = 25°C |
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WDFN-10L 3x3 ------------------------------------------------------------------------------------------------------------- |
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0.952W |
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WQFN-12L 2x2 ------------------------------------------------------------------------------------------------------------ |
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0.606W |
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Package Thermal Resistance (Note 2) |
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WDFN-10L 3x3, θJA ------------------------------------------------------------------------------------------------------- |
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105°C/W |
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WDFN-10L 3x3, θJC ------------------------------------------------------------------------------------------------------- |
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8.2°C/W |
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WQFN-12L 2x2, θJA ------------------------------------------------------------------------------------------------------- |
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165°C/W |
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Lead Temperature (Soldering, 10 sec.) ------------------------------------------------------------------------------- |
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260°C |
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Junction Temperature ----------------------------------------------------------------------------------------------------- |
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150°C |
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Storage Temperature Range -------------------------------------------------------------------------------------------- |
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−65°C to 150°C |
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ESD Susceptibility (Note 3) |
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HBM (Human Body Model) ---------------------------------------------------------------------------------------------- |
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2kV |
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MM (Machine Model) ----------------------------------------------------------------------------------------------------- |
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200V |
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Recommended Operating Conditions (Note 4) |
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Input Voltage, VIN ---------------------------------------------------------------------------------------------------------- |
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4.5V to 26V |
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Control Voltage, VCC ------------------------------------------------------------------------------------------------------ |
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4.5V to 5.5V |
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Junction Temperature Range -------------------------------------------------------------------------------------------- |
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−40°C to 125°C |
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Ambient Temperature Range -------------------------------------------------------------------------------------------- |
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−40°C to 85°C |
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Electrical Characteristics |
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(VCC = 5V, TA = 25°C, unless otherwise specified) |
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Parameter |
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Symbol |
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Test Conditions |
Min |
Typ |
Max |
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Unit |
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Input Power Supply |
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VCC Quiescent Supply |
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IQ |
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FB |
forced above the |
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500 |
1250 |
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A |
Current |
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point, VEN = 5V, |
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VCC Shutdown Current |
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ISHDN |
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VCC current, VEN = 0V |
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1 |
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A |
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CS Shutdown Current |
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CS pull to GND |
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-- |
1 |
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A |
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FB Error Comparator |
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VREF |
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DEM |
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0.7005 |
0.704 |
0.7075 |
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V |
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Threshold |
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DEM, TA = 40 to 85 C |
(Note 5) |
0.697 |
0.704 |
0.711 |
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FB Input Bias Current |
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VFB = 0.735V |
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1 |
0.01 |
1 |
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A |
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Copyright ©2014 Richtek Technology Corporation. All rights reserved. |
is a registered trademark of Richtek Technology Corporation. |
www.richtek.com |
DS8237C/D-06 February 2014 |
4 |
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RT8237C/D
Parameter |
Symbol |
Test Conditions |
Min |
Typ |
Max |
Unit |
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VOUT Voltage Range |
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0.7 |
-- |
3.3 |
V |
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RRF = 470k |
(Note 6) |
-- |
290 |
-- |
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Switching Frequency |
fSW |
RRF = 200k |
(Note 6) |
-- |
340 |
-- |
kHz |
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RRF = 100k |
(Note 6) |
-- |
380 |
-- |
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RRF = 39k |
(Note 6) |
-- |
430 |
-- |
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Minimum Off-Time |
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250 |
400 |
550 |
ns |
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Current Sensing |
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CS Source Current |
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ICS |
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9 |
10 |
11 |
A |
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CS Source Current TC |
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-- |
4700 |
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ppm/ C |
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Zero Crossing Threshold |
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DEM |
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10 |
-- |
5 |
mV |
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GND PHASE, VCS = 2.4V |
280 |
300 |
320 |
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Current Limit Threshold |
VLIMIT |
GND PHASE, VCS = 1.6V |
185 |
200 |
215 |
mV |
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GND PHASE, VCS = 0.4V |
40 |
50 |
60 |
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Negative Current Limit |
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PHASE GND, VCS = 2.4V |
-- |
300 |
-- |
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-- |
200 |
-- |
mV |
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Threshold |
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PHASE GND, VCS = 1.6V |
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PHASE GND, VCS = 0.4V |
-- |
50 |
-- |
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Protection Function |
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Output UV Threshold |
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With respect to error |
65 |
70 |
75 |
% |
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comparator threshold |
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OVP Threshold |
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With respect to error |
120 |
125 |
130 |
% |
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comparator threshold |
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||
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. |
DS8237C/D-06 February 2014 |
www.richtek.com |
|
5 |
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 |
6 |
|