T
echcode
®
2.4A 32V Synchronous Rectified Step-Down Converter
DATASHEET
TD2778
General Description
The TD2778 is a monolithic synchronous buck
regulator. The device integrates two 90mΩ
MOSFETs, and provides 2.4A of continuous load
current over a wide input voltage of 4.75V to 32V.
Current mode control provides fast
transient
response and cycle-by-cycle current limit.
An adjustable soft-start prevents inrush current at
turn-on, and in shutdown mode the supply current
drops to 1µA.
This device, available in an SOP8-PP package,
provides a very compact solution with minimal external
components.
Features
•
•
•
•
•
•
•
•
•
•
2.4A Output Current
Wide 4.75V to 32V Operating Input Range
Integrated 90mΩ Power MOSFET Switches
Output Adjustable from 0.923V to 30V
Up to 93% Efficiency
Programmable Soft-Start
Stable with Low ESR Ceramic Output Capacitors
Fixed 200KHz
Cycle-by-Cycle Over Current Protection
Input Under Voltage Lockout
Applications
•
•
•
•
•
Distributed Power Systems
Networking Systems
FPGA, DSP, ASIC Power Supplies
Green Electronics/ Appliances
Notebook Computers
Package Types
Figure 1. Package Types of TD2778
October, 20, 2010.
Techcode Semiconductor Limited
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SOP8
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T
echcode
®
2.4A 32V Synchronous Rectified Step-Down Converter
DATASHEET
TD2778
Pin Configurations
Figure 2 Pin Configuration of TD2778(Top View)
Pin Description
Pin Number
Pin Name
Description
High-Side Gate Drive Boost Input. BS supplies the drive for the high-side N-Channel
1
BS
MOSFET switch. Connect a 0.01µF or greater capacitor from SW to BS to power the
high side switch.
Power Input. IN supplies the power to the IC, as well as the step-down converter
2
IN
switches. Drive IN with a 4.75V to 32V power source. Bypass IN to GND with a
suitably large capacitor to eliminate noise on the input to the IC. See
Input Capacitor.
Power Switching Output. SW is the switching node that supplies power to the output.
3
4
5
SW
GND
FB
Connect the output LC filter from SW to the output load. Note that a capacitor is
required from SW to BS to power the high-side switch.
Ground.
Feedback Input. FB senses the output voltage to regulate that voltage. Drive FB
with a resistive voltage divider from the output voltage. The feedback threshold
is 0.923V. See
Setting the Output Voltage.
Compensation Node. COMP is used to compensate the regulation control loop.
Connect a series RC network from COMP to GND to compensate the regulation
control loop. In some cases, an additional capacitor from COMP to GND is
required. See
Compensation Components.
Enable Input. EN is a digital input that turns the regulator on or off. Drive EN high to
6
COMP
7
EN
turn on the regulator, drive it low to turn it off. Pull up with 100kΩ resistor for
automatic startup.
Soft-Start Control Input. SS controls the soft start period. Connect a capacitor from SS
8
SS
to GND to set the soft-start period. A 0.1µF capacitor sets the soft-start period to 15ms.
To disable the soft-start feature, leave SS unconnected.
October, 20, 2010.
Techcode Semiconductor Limited
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T
echcode
®
2.4A 32V Synchronous Rectified Step-Down Converter
DATASHEET
TD2778
Ordering Information
TD2778
Circuit Type
□
□
Packing:
Blank：Tube
R:Type and Reel
Package
M:SOP8-PP
Function Block
Figure 3 Function Block Diagram of TD2778
October, 20, 2010.
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T
echcode
®
2.4A 32V Synchronous Rectified Step-Down Converter
DATASHEET
TD2778
Absolute Maximum Ratings
Parameter
Symbol
V
IN
V
SW
V
BS
V
OUT
Value
-0.3 to 32
30
Unit
V
V
V
V
V
º
C
º
C
º
C
V
º /W
C
º /W
C
Supply Voltage
Switch Node Voltage
Boost Voltage
Output Voltage
All Other Pins
Operating Junction Temperature
Storage Temperature
Lead Temperature (Soldering, 10 sec)
ESD (HBM)
MSL
Thermal Resistance-Junction to Ambient
Thermal Resistance-Junction to Case
V
SW
– 0.3V to
V
SW
+6V
0.923V to 30
–0.3V to +6V
T
J
T
STG
T
LEAD
150
-65 to 150
260
2000
RθJA
RθJC
Level3
90
45
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T
echcode
®
2.4A 32V Synchronous Rectified Step-Down Converter
DATASHEET
TD2778
Electrical Characteristics
V
IN
= 12V, T
a
= 25℃ unless otherwise specified.
Parameters
Shutdown Supply Current
Supply Current
Feedback Voltage
Feedback Overvoltage Threshold
Error Amplifier Voltage Gain *
Error Amplifier Transconductance
High-Side Switch On Resistance *
Low-Side Switch On Resistance *
High-Side Switch Leakage
Current
Upper Switch Current Limit
Lower Switch Current Limit
COMP to Current Sense
Transconductance
Oscillation Frequency
Short Circuit Oscillation
Frequency
Maximum Duty Cycle
Minimum On Time *
EN Shutdown Threshold Voltage
EN Shutdown Threshold Voltage
Hysteresis
EN Lockout Threshold Voltage
EN Lockout Hysterisis
Symbol
Test Condition
VEN = 0V
VEN = 2.0V; VFB =
1.0V
Min.
Typ.
1
1.3
Max.
3.0
1.5
0.946
Unit
µA
mA
V
V
V/V
µA/V
mΩ
mΩ
VFB
4.75V ≤ VIN ≤30V
0.900
0.923
1.1
AEA
GEA
RDS(ON)1
RDS(ON)2
VEN = 0V, VSW = 0V
Minimum Duty Cycle
From Drain to Source
GCS
∆IC = ±
10µA
400
800
90
90
10
2.9
1.1
µA
A
A
4.8
TD2778
200
A/V
KHz
Fosc1
Fosc2
DMAX
VFB = 0V
VFB = 1.0V
100
90
220
KHz
%
ns
2.0
V
VEN Rising
1.1
1.5
210
2.2
2.5
210
2.7
mV
V
mV
October, 20, 2010.
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stm32/stm8
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