Richtek RT8237CZQW, RT8237DZQW Schematic [ru]

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®
RT8237C/D
High Efficiency Single Synchronous Buck PWM Controller
General Description
The RT8237C/D PWM controller provides high efficiency , excellent transient response, a nd high DC output a ccuracy 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 ha ndles wide input/output voltage ratios with ea se and provides 100ns instant-on response to load transients while maintaining a relatively constant switching frequency .
The RT8237C/D 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 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 a s low a s 0.7V . The RT8237C is available in a W DF N-10L 3x3 package, The R T8237D 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/

Side R

4 Selectable Frequency Setting


Soft-Start Control


Drives Large Synchronous-Rectifier FET s


Integrated Boot Switch


Built-in OVP/OCP/UVP


Thermal Shutdown


Power Good Indicator


RoHS Compliant and Halogen Free

°°
°C Programmable Current Limit by Low
°°
Sensing
DS(ON)
Applications
Notebook ComputersCPU Core SupplyChipset/RAM Supply a s Low as 0.7VGeneric DC/DC Power Regulator
Pin Configurations
(TOP VIEW)
GND
11
10
9 8 7 6
BOOT UGATE PHASE VCC LGATE
Ordering Information
RT8237
(2)
Pin 1 Orientation (2) : Quadrant 2, Follow EIA-481-D
Package Type
PGOOD
CS EN
FB
RF
1 2 3 4 5
WDFN-10L 3x3
RT8237C
QW : WDFN-10L 3x3 (W-Type) QW : WQFN-12L 2x2 (W-Type)
Lead Plating System Z : ECO (Ecological Element with Halogen Free and Pb free)
C : WDFN-10L 3x3
LGATE FB
VCC
PHASE
D : WQFN-12L 2x2
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. is a registered trademark of Richtek Technology Corporation.
DS8237C/D-06 February 2014 www.richtek.com
©
GNDNCRF
12 1011
1
GND
2 3
13
BOOT
UGATE
654
PGOOD
WQFN-12L 2x2
RT8237D
9 8
EN
7
CS
1
RT8237C/D
Marking Information
RT8237CZQW
Z3 : Product Code
Z3 YM
DNN
Typical Application Circuit
R1
V
0
CC
Chip Enable
YMDNN : Date Code
C1
R5
1µF
100k
16V
R
RF
R
470k
:
*
OC_SET
30k
l
a
n
i
o
t
p
O
V
P
EN
RF
C
G
R
T
3
8
2
7
C
/
C
C
O
G
S
D
N
B
U
G
D
O
P
H
L
RT8237DZQW
72 : Product Code
72W
V
C
BOOT
0
R
LGATE
R
UGATE
0
0.1µF 50V
0
R
D
O
A
A
G
BOOT
O
T
T
E
S
E
A
T
E
F
B
IN
W : Date Code
C2 10µF x 3 50V
L
OUT
0.45µH
R2*
C3*
R
FB1
5.1k
R
FB2
10k
R3*
C4*
V
OUT
1.05V
C6 10µF x 2 16V
C5*
C
OUT
330µF x 2 16V
Functional Pin Description
Pin No.
RT8237C RT8237D
1 6 PGOOD
2 7 CS
3 8 EN PWM Enable. Pull low to GND to disable the PWM. 4 9 FB
5 10 RF
6 1 LGATE Gate Drive Output for Low S ide External MOSFET.
7 2 VCC
Pin Name Pi n Func t i o n
Open Drain Power Good Indicator. High impedance indicates power is good.
Curren t Li mit Thr eshold Setting I nput . Connect a setti ng r esi stor to GND and the current limit threshold is equal to 1/8 of the volt age at this pin.
Feedback Input. Connect FB to a resistor voltage divider
V
OUT
fro m V
to GND to adjust the output from 0.7V to 3.3V
OUT
Switching Frequency Selection. Connect a resistance to select switching frequency as shown in Electrical Charac t er istics. The swi t c hin g frequency is det ect ed and latched af ter start up. This pin also cont rols Diode emulat ion mode or forced C CM selection. Pull down to GND with resistor : Diode Emulation Mode. Connect to PGOOD with resistor : forced CCM after PGOOD becomes hi gh.
Contr ol Voltage Input. This pin provides the power for the buck contr oller, the low si de dr iv er an d th e bootstrap ci rcuit for high side dri v er. Byp ass to GND wi th a 1F ceramic capa citor.
Copyright 2014 Richtek Technology Corporation. All rights reserved. is a registered trademark of Richtek Technology Corporation.
©
DS8237C/D-06 February 2014www.richtek.com
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RT8237C/D
Pin No.
Pin Name Pi n Func t i o n
RT8237C RT8237D
8 3 PHASE
9 4 UGATE Gate Drive Output for High Side Exter nal MOSFET.
10 5 BOOT
--- 11 NC No Internal Connection. 11
(Expo sed Pad)
12, 13
(Exp osed Pad)
GND
Function Block Diagram
TRIG
RF
PHASE
On-time
Compute
1-SHOT
External Inductor C onnection Pin for PWM Converter. It behaves as the current sense comparator input for low side MOSFET R
sensing and r eference voltage for on time generation.
DS(ON)
Supply Input for High Si de Driver. Connect through a capacitor to the float ing node (PHASE) pin.
Ground. The exposed pad must be soldered to a large PCB and conn ect ed to GND for maxim um power dissipation.
VCC
COMP
­+
R
QS
PWM
DRV
BOOT
UGATE
FB
VCC
EN
CS
POR
10µA
125%
V
REF
70%
V
REF
Timer
SS
+
-
+
-
V
REF
OV
UV
125% V
90% V
Latch
S1 Q
Latch
S1 Q
-
REF
+
­+
REF
Thermal
Shutdown
Min. t
OFF
QTRIG
1-SHOT
DEM/FCCM
­+
X(1/8)
+
-
X(-1/8)
DRV
PHASE
LGATE GND
PGOOD
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
Absolute Maximum Ratings (Note 1)
VCC, FB, PGOOD, EN, CS, RF to GND ---------------------------------------------------------------------------- 0.3V to 6VBOOT to PHASE ---------------------------------------------------------------------------------------------------------- 0.3V to 6VPHASE to GND
DC----------------------------------------------------------------------------------------------------------------------------- 0.3V to 32V <20ns ------------------------------------------------------------------------------------------------------------------------ 8V to 38V
UGA TE to PHASE -------------------------------------------------------------------------------------------------------- −0.3V to 6V
DC----------------------------------------------------------------------------------------------------------------------------- 0.3V to 6V <20ns ------------------------------------------------------------------------------------------------------------------------ 5V to 7.5V
LGA TE to GN D ------------------------------------------------------------------------------------------------------------- −0.3V to 6V
DC----------------------------------------------------------------------------------------------------------------------------- 0.3V to 6V <20ns ------------------------------------------------------------------------------------------------------------------------ 2.5V to 7.5V
Power Dissipation, P
W D FN-10L 3x3------------------------------------------------------------------------------------------------------------- 0.952W WQFN-12L 2x2 ------------------------------------------------------------------------------------------------------------ 0.606W
Package Thermal Re sistance (Note 2)
W DFN-10L 3x3, θJA------------------------------------------------------------------------------------------------------- 105°C/W WDFN-10L 3x3, θJC------------------------------------------------------------------------------------------------------- 8.2°C/W
WQFN-12L 2x2, θJA------------------------------------------------------------------------------------------------------- 165°C/W
Lead Temperature (Soldering, 10 sec.)------------------------------------------------------------------------------- 260°CJunction T emperature----------------------------------------------------------------------------------------------------- 150°CStorage T emperature Range -------------------------------------------------------------------------------------------- 65°C to 150°CESD Susceptibility (Note 3)
HBM (Human Body Model)---------------------------------------------------------------------------------------------- 2kV MM (Machine Model) ----------------------------------------------------------------------------------------------------- 200V
@ TA = 25°C
D
Recommended Operating Conditions (Note 4)
Input Voltage, VControl Voltage, VJunction T emperature Range-------------------------------------------------------------------------------------------- 40°C to 125°CAmbient T emperature Range-------------------------------------------------------------------------------------------- 40°C to 85°C
---------------------------------------------------------------------------------------------------------- 4.5V to 26V
IN
------------------------------------------------------------------------------------------------------ 4.5V to 5.5V
CC
Electrical Characteristics
(VCC = 5V, T
Input Power Supply
VCC Quiescent Supply Current
VCC Shutdown Current I CS Shutdown Curr ent CS pull to GND -- -- 1 A
FB Error Co mp arator Threshold
FB Input Bias Current V
Copyright 2014 Richtek Technology Corporation. All rights reserved. is a registered trademark of Richtek Technology Corporation.
4
= 25°C, unless otherwise specified)
A
Parameter Symbol Test Conditions Min Typ Max Unit
I
Q
SHDN
FB forced above the regulation point, V
= 5V,
EN
VCC current, VEN = 0V -- -- 1 A
-- 500 1250 A
DEM 0.7005 0.704 0.7075
V
REF
©
DEM, TA = 40 to 85C (Note 5) 0.697 0.704 0.711
= 0.735V 1 0.01 1 A
FB
DS8237C/D-06 February 2014www.richtek.com
V
RT8237C/D
Parameter Symbol Test Conditions Min Typ Max Unit
V
Voltage Range 0.7 -- 3.3 V
OUT
RRF = 470k (Note 6) -- 290 --
Switc hing Fre quen cy f
SW
Minimum Off-Time 250 400 550 ns
Current Sensing
CS Source Current ICS 9 10 11 A CS Source Current TC -- 4700 -- ppm/C Zero Crossing Thresho ld DEM 10 -- 5 mV
Cu rrent Lim it T hr eshol d V
LIMIT
PHASE GND, VCS = 2.4V -- 300 --
Negative Current Limit Threshold
PHASE GND, VCS = 1.6V -- 200 -­ PHASE GND, V
Protection Function
Output UV Threshold
OVP Threshold OV Fault Delay FB forc ed above OV threshold -- 5 -- s VCC Under Voltage Lockout
Threshold V
Soft-Start From EN = high to V
OUT
UVLO
UV Blank Time From EN signal going high -- 3 -- ms Ther mal Shut dow n TSD -- 150 -- C
Driver On Resistance
UGATE Drive Source R UGATE Drive Sink R LGATE Drive Source R LGATE Drive Sink R
Dead Time
UGATEsr UGATEsk LGATEsr LGATEsk
LGATE R ising (V UGATE Rising -- 30 --
Internal Boost Charging Switch On Resistance
VCC to BOOT, 10 mA -- -- 8 0
EN Threshold
EN Input Threshold Voltage
Logic-High VIH 1.8 -- -­Logic-Low V
-- -- 0.5
IL
RRF = 200k (Note 6) -- 340 --
kHz
RRF = 100k (Note 6) -- 380 -­RRF = 39k (Note 6) -- 430 --
GND PHASE, V GND PHASE, VCS = 1.6V 185 200 215
= 2.4V 280 300 320
CS
mV
GND PHASE, VCS = 0.4V 40 50 60
mV
= 0.4V -- 50 --
CS
With respect to error comparator threshold
With respect to error comparator threshold
65 70 75 %
120 125 130 %
Falling edge, hysteresis = 100mV, PWM
3.7 3.9 4.1 V
disabled below this level
= 95% -- 1300 -- s
OUT
BOOT  PHASE forced to 5V -- 1.8 3.6
BOOT PHA SE forced to 5V -- 1.2 2.4
LG ATE, High State -- 1.8 3.6
LGATE, Low State -- 0.8 1.6
= 1.5V) -- 30 --
PHASE
ns
V
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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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
Tr ip Thres ho ld (fa lli ng, leaving PGOOD)
Trip Threshold (rising, leaving PGOOD)
Fault Propagation Delay Output Low Voltage I
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. θ
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 V
is measured at T
JA
measured at the exposed pad of the package.
= 25°C on a low effective thermal conductivity single-layer test board per JEDEC 51-3. θJC is
A
Measured at FB, with respect to referenc e, Hysteresis = 3%
Measured at FB, with respect to reference,
Hys teresis = 3%
Falling Edge, FB forced below PGOOD trip threshold
= 1m A -- -- 0.4 V
SINK
= 8V, V
IN
= 1.1V, I
OUT
= 10A using application circuit.
OUT
87 90 93 %
120 125 130 %
-- 2.5 -- s
Copyright 2014 Richtek Technology Corporation. All rights reserved. is a registered trademark of Richtek Technology Corporation.
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