T
echcode
®
3A 30V Synchronous Rectified Step-Down Converter
Features
DATASHEET
TD2786
General Description
TD2786 is a 3A synchronous buck converter with integrated
power MOSFETs. The TD2786 design with a current‐mode
control scheme, can convert wide input voltage of 4.5V to
30V to the output voltage adjustable from 0.92V to 28V to
provide excellent output voltage regulation.
The TD2786 is equipped with an automatic PFM/PWM mode
operation. At light load, the IC operates in the PFM mode to
reduce the switching losses. At heavy load, the IC works in
PWM mode.
The TD2786 is also equipped with Power‐on‐reset, soft‐ start,
and whole protections (over‐temperature, and current‐limit)
into a single package.
This device, available ESOP‐8, provides a very compact
system solution external components and PCB area.
Wide Input Voltage from 4.5V to 30V
3A Continuous Output Current
Adjustable Output Voltage from 0.92V to 28V
Integrated N‐MOSFET
Fixed 340kHz Switching Frequency
PFM/PWM mode Operation
Stable with Low ESR Capacitors
Power‐On‐Reset Detection
Programmable Soft‐Start
Over‐Temperature Protection
Over‐Voltage Protection
Current‐Limit Protection with Frequency Foldback
Enable/Shutdown Function
Lead Free and Green Devices Available(RoHS
Compliant)
Applications
Distributed Power Systems
Networking Systems
FPGA, DSP, ASIC Power Supplies
Green Electronics/ Appliances
Notebook Computers
Pin Configurations
Figure1 Pin Configuration of TD2786(Top View)
July, 29, 2014.
Techcode Semiconductor Limited
www.techcodesemi.com
1
T
echcode
®
3A 30V Synchronous Rectified Step-Down Converter
DATASHEET
TD2786
Pin Description
Pin Number
Pin Name
Description
High‐Side Gate Drive Boost Input. BS supplies the voltage to drive the high‐side
N‐channel MOSFET. At least 10nF capacitor should be connected from SW to BS to
supply the high side switch.
Power Input. VIN supplies the power (4.5V to 30V) to the control circuitry, gate drivers
and step‐down converter switches. Connecting a ceramic bypass capacitor and a
suitably large capacitor between VIN and GND eliminates switching noise and voltage
ripple on the input to the IC.
Power Switching Output. SW is the Drain of the N‐Channel power MOSFET to supply
power to the output LC filter.
Ground.
Output feedback Input. The TD2786 senses the feedback voltage via FB and regulates
the voltage at 0.92V. Connecting FB with a resistor‐divider from the converter’s output
sets the output voltage from 0.92V to 28V.
Output of the error amplifier. 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.
Enable Input. EN is a digital input that turns the regulator on or off. Pull up with 100k
resistor for automatic startup.
Soft‐Start Control Input. SS controls the soft‐start period. Connect a capacitor from 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.
1
BS
2
VIN
3
4
5
SW
GND
FB
6
COMP
7
EN
8
SS
Ordering Information
TD2786
□
Circuit Type
Packing:
Blank: Tube
R: Tape and Reel
Package
M:ESOP-8
□
July, 29, 2014.
Techcode Semiconductor Limited
www.techcodesemi.com
2
T
echcode
®
3A 30V Synchronous Rectified Step-Down Converter
DATASHEET
TD2786
Function Block
Figure 2 Function Block Diagram of TD2786
Absolute Maximum Ratings
Parameter
Input Voltage
SW Pin GND Voltage
EN,FB,COMP,SS to GND Voltage
BS to GND Voltage
Power Dissipation
Operating Junction Temperature
Storage Temperature
Lead Temperature
symbol
V
IN
V
SW
V
BS
P
D
T
J
T
STG
T
LEAD
Value
‐0.3 to 32
‐0.3 to V
IN
+0.3
‐0.3 to 6
V
SW
‐0.3 to V
SW
+6
Internally limited
150
‐65 to 150
260
Unit
V
V
V
V
mW
℃
℃
℃
July, 29, 2014.
Techcode Semiconductor Limited
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T
echcode
®
3A 30V Synchronous Rectified Step-Down Converter
θ
JA
θ
JC
2000
Level3
50
10
DATASHEET
TD2786
V
℃/W
℃/W
ESD (HBM)
MSL
Junction to Ambient Resistance in Free Air
Junction to Case Resistance in Free Air
Recommended Operating Conditions
Parameter
Input voltage
Output voltage
Converter output current
Operating junction temperature
Operating ambient temperature
Symbol
V
IN
V
out
I
out
T
J
T
A
Min.
4.5
0.925
0
‐40
‐40
Max.
30
28
3
125
85
Unit
V
V
A
℃
℃
Electrical Characteristics
V
IN
=12V, Vout=3.3V，V
EN
=3V,TA =+25℃, unless otherwise noted
Parameter
Symbol
SUPPLY CURRENT
VIN Supply Current
I
VIN
VIN Shutdown Supply Current
I
VIN_SD
POWER‐ON‐RESET (POR)
VIN POR Voltage Threshold
VIN POR Hysteresis
REFERENCE VOLTAGE
Reference Voltage
V
REF
OSCILLATOR AND DUTY CYCLE
Oscillator Frequency
F
OSC
Foldback Frequency
Maximum Converter’s Duty
Minimum On Time
PFM MODE OPERATION
PFM Mode Current Limit
I
PK_PFM
PWM to PFM Inductor Peak Threshold I
PK_TH
POWER MOSFET
High/low Side MOSFET On Resistance
High/Low Side MOSFET Leakage
Current
Condition
V
FB
=1V, V
EN
=3V, SW=NC
V
EN
=0V
V
IN
Rising
Regulated on FB pin
V
FB
=0V
V
EN
=0V, V
LX
=0V
Min
‐
‐
3.8
‐
0.9
300
‐
‐
‐
‐
‐
‐
‐
Typ
1.9
0.3
4.1
0.3
0.92
340
110
90
220
0.8
0.6
110
‐
Max
‐
‐
4.4
‐
0.946
380
‐
‐
‐
‐
‐
‐
10
Units
mA
uA
V
V
V
kHz
kHz
%
ns
A
A
mΩ
uA
July, 29, 2014.
Techcode Semiconductor Limited
www.techcodesemi.com
4
T
echcode
®
3A 30V Synchronous Rectified Step-Down Converter
COMP=NC
‐
‐
‐
DATASHEET
TD2786
820
80
5.2
‐
‐
‐
uA/V
V/V
A/V
CURRENT‐MODE PWM CONVERTER
Error Amplifier Transconductance
Gm
Error Amplifier Voltage Gain
Switch Current to COMP Voltage
Transconductance
PROTECTIONS
High Side MOSFET Current‐Limit
I
LIM
Over‐Temperature Trip Point
T
OTP
Over‐Temperature Hysteresis
Over‐Voltage Protection
SOFT‐START, ENABLE AND INPUT CURRENTS
Soft‐Start Current
EN Enable Threshold Voltage
EN Under‐Voltage Lockout (UVLO)
Threshold
EN UVLO Hysteresis
Peak Current
VIN=4.5~28V
V
EN
rising
‐
‐
‐
‐
‐
0.4
2.3
‐
5.6
160
50
120
6
‐
2.5
200
‐
‐
‐
‐
‐
2
2.7
‐
A
℃
℃
%
uA
V
V
mV
July, 29, 2014.
Techcode Semiconductor Limited
www.techcodesemi.com
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