RT8110 Datasheet PDF - RICHTEK

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RT8110
RICHTEK

Part Number RT8110
Description Compact Synchronous Buck DC/DC PWM Controller
Page 14 Pages


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RT8110
Compact Synchronous Buck DC/DC PWM Controller
General Description
The RT8110 is a compact fixed-frequency PWM controller
with integrated MOSFET drivers for single-phase
synchronous buck converter. This part features wide input
voltage range operation and tiny package. An internal pre-
regulator drives an external BJT to provide regulated output
voltage from the input voltage to support VCC. Therefore,
the controller can operate with wide input voltage range.
The RT8110 utilizes voltage-mode control with internal
compensation to simplify the converter design. An internal
0.8V reference voltage allows low output voltage
application. The switching frequency is fixed at 400kHz
to reduce the external passive component size to save
board space. Low-side MOSFET RDS(ON) is used for
inductor current sensing. The RT8110 provides under
voltage protection, current limit, over current protection
and over temperature protection.
Ordering Information
RT8110
Package Type
J8 : TSOT-23-8
Operating Temperature Range
P : Pb Free with Commercial Standard
G : Green (Halogen Free with Commer-
cial Standard)
Note :
Richtek Pb-free and Green 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.
Features
z 8V to 23V Wide Range Operation
z 0.8V Internal Reference
z Internal Soft Start
z High DC Gain Voltage Mode PWM Control
z Fixed 400kHz Switching Frequency
z Fast Transient Response
z Fully Dynamic 0 to 80% Duty Cycle
z Over Current Protection
z Under Voltage Protection
z Over Temperature Protection
z Tiny Package TSOT-23-8
z RoHS Compliant and 100% Lead (Pb)-Free
Applications
z Set-top Box Power Supplies
z PC Subsystem Power Supplies
z Cable Modems, DSL Modems
z DSP and Core Communication Processor Power
Supplies
z Memory Power Supplies
z Personal Computer Peripherals
z Industrial Power Supplies
z Low Voltage Distributed Power Supplies
Pin Configurations
(TOP VIEW)
Marking Information
For marking information, contact our sales representative
directly or through a Richtek distributor located in your
area, otherwise visit our website for detail.
87 6 5
2 34
TSOT-23-8
DS8110-00 May 2009
www.richtek.com
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RT8110
Typical Application Circuit
VIN
8V to 23V
DBOOT
R
CVCC
Shutdown
Q2
RT8110
2 DRIVE BOOT 1
4 VCC
UGATE 7
PHASE 8
3 FB
LGATE 5
GND 6
R1
R2
C3 R3
CBOOT
CIN
MU
L1
ML
COUT
Figure 1. Single Input Power Rail Application
DBOOT
RX
5V
CVCC
Shutdown
Q1
RT8110
2 DRIVE BOOT 1
UGATE 7
4 VCC
PHASE 8
3 FB
LGATE 5
GND 6
R1
VIN
5V to 23V
CBOOT
CIN
MU
L1
ML
COUT
R2
C3 R3
Figure 2. Split Input Power Rail Application
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RT8110
Functional Pin Description
Pin No. Pin Name
Pin Function
1 BOOT
This pin provides power to the high-side MOSFET gate driver. Use bootstrap circuit to drive
the high-side MOSFET.
Pre-regulator Control Pin. Connect this pin to the base of external BJT, and connect the
collector to VIN to obtain a regulated output voltage to support VCC. If VCC is directly
2 DRIVE supplied, the BJT is not required, and this pin should be pulled high to VCC through a
resistor. DRIVE pin can also be used for enable control. Pull low this pin to GND can
shutdown the controller.
3 FB
Inverting Input of the Error Amplifier. This pin is connected to the joint of output voltage
divider resistors to set the output voltage. The voltage at this pin is also monitored for under
voltage protection.
4 VCC
Main Bias Supply of the IC. VCC can be directly supplied or by VIN through external BJT
driven by DRIVE pin. This pin also provides power for the low-side MOSFET gate driver.
Connect ceramic capacitor to this pin. The voltage at this pin is monitored for power on
reset (POR).
5 LGATE Gate Drive Pin for Low-Side MOSFET.
6 GND
Signal and Power Ground of the IC. All voltage levels are referenced with respect to this pin.
7 UGATE Gate Drive Pin for High-Side MOSFET.
8
PHASE
Switching Node of the Buck Converter. This pin is also used to monitor the voltage drop
across the low-side MOSFET for over current protection.
Function Block Diagram
DRIVE VCC
VCC
0.8VREF
SS
VCC
Pre-Regulator
Power-
On Reset
POR
0.5V
UVP
-
+
Soft-Start
and Fault
Logic
S1L
IOC
OC
+
-
-
+
PH_M
ROC
1.5V
FB
++Gm EO
-
+
Gate
Control
-
PWM
Logic
VCC
Oscillator
PHASE
UGATE
BOOT
LGATE
GND
DS8110-00 May 2009
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RT8110
Absolute Maximum Ratings (Note 1)
z Supply Voltage, VCC ---------------------------------------------------------------------------------------------- 7V
z PHASE -------------------------------------------------------------------------------------------------------------- 3V to 24V
z BOOT ---------------------------------------------------------------------------------------------------------------- 30V
z Input/Output Voltage ---------------------------------------------------------------------------------------------- 0.3V to 7V
z Power Dissipation, PD @ TA = 25°C
TSOT-23-8 ----------------------------------------------------------------------------------------------------------- 0.426W
z Package Thermal Resistance (Note 4)
TSOT-23-8, θJA ----------------------------------------------------------------------------------------------------- 235°C/W
z Junction Temperature --------------------------------------------------------------------------------------------- 150°C
z Lead Temperature (Soldering, 10 sec.) ----------------------------------------------------------------------- 260°C
z Storage Temperature Range ------------------------------------------------------------------------------------ 65°C to 150°C
z ESD Susceptibility (Note 2)
HBM (Human Body Mode) -------------------------------------------------------------------------------------- 2kV
MM (Machine Mode) ---------------------------------------------------------------------------------------------- 200V
Recommended Operating Conditions (Note 3)
z Supply Voltage, VCC ---------------------------------------------------------------------------------------------- 5.3V
z Junction Temperature Range ------------------------------------------------------------------------------------ 40°C to 125°C
z Ambient Temperature Range ------------------------------------------------------------------------------------ 40°C to 85°C
Electrical Characteristics
(VIN = 5V, TA = 25°C, unless otherwise specified)
Parameter
Symbol
Test Conditions
VCC Supply Current
Nominal Supply Current
Regulated Output Voltage
Power-On Reset
VCC Threshold Voltage
VCC Threshold Hysteresis
ICC
VCC
UGATE, LGATE open
Ris in g
Reference
Reference Voltage
VREF
Oscil lator
Free Running Frequency
Ramp Amplitude
Error Amplifier
fSW
Δ VOSC
E/A Transconductance
Gm
Note 5
Open Loop DC Gain
AO Note 5
PWM Controller Gate Driver
Upper Drive Source
RUS OURCE
VBOOT PHASE = 5V
VBOOT VUGATE = 1V
Min Typ Max Units
-- 3 6 mA
5.1 5.3 5.5 V
3.6 3.9 4.2
0.3 0.5 0.7
V
V
0.784 0.8 0.816 V
320 400 480 kHz
-- 2.2 -- V
-- 0.3 -- ms
60 90 -- dB
-- 3 4.5 Ω
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To be continued
DS8110-00 May 2009
Free Datasheet http://www.datasheet4u.com/



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