TD8002
High Efficiency 1MHz 2A
Synchronous Step Down Regulator
TITAN MICRO
Description
Features
The TD8002 is a high efficiency, high frequency
synchronous DC-DC step-down converter. The
100% duty cycle feature provides low dropout
operation, extending battery life in portable systems.
The internal synchronous switch increases efficiency
and eliminates the need for external Schottky diode.
At shutdown mode, the input supply current is less
than 1µA.
The current limit protection and on-chip thermal
shutdown features provide protection against any
combination of overload or ambient temperature.
Low RDS(ON) for Internal Switch (Top/Bottom):
180/100mΩ
2.5V~5.5V Input Voltage Range
2A Output Current
1MHz Switching Frequency Minimizes the
External Components
Internal Soft-Start Limits the Inrush Current
Internal Compensation Function
100% Dropout Operation
Power Good Indicator Output (SOT-23-6 only)
RoHS Compliant and Halogen Free
SOT-23-5 and SOT-23-6 Packages
Applications
Set Top Box
LCD TV
Tablet
Portable Equipment
Pin Assignments
S5 Package (SOT-23-5)
FB
VIN
5
4
(Marking)
1
2
3
EN GND LX
S6 Package (SOT-23-6)
FB
PG VIN
6
5
4
(Marking)
1
2
3
EN GND LX
Figure 1. Pin Assignment of TD8002
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TD8002
High Efficiency 1MHz 2A
Synchronous Step Down Regulator
TITAN MICRO
/a85T
Typical Application Circuit
OFF ON
EN
L1
VIN
VIN
LX
VOUT
TD8002
C1
R1
C3
C2
(opt.)
FB
GND
R2
Figure 2. Schematic Diagram
VOUT
3.3V
2.5V
1.8V
1.5V
1.2V
1.05V
C1
10μF MLCC
10μF MLCC
10μF MLCC
10μF MLCC
10μF MLCC
10μF MLCC
R1
453kΩ
316kΩ
200kΩ
150kΩ
100kΩ
75kΩ
R2
100kΩ
100kΩ
100kΩ
100kΩ
100kΩ
100kΩ
L1
μH
μH
1.8μH
1.5μH
1.5μH
1.2μH
C2
22μF MLCC
22μF MLCC
22μF MLCC
22μF MLCC
22μF MLCC
22μF MLCC
Table 1. Recommended Component Values
Ordering Information
Part number
Package
TD8002 ES5
SOT-23-5
TD8002 ES6
SOT-23-6
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TD8002
High Efficiency 1MHz 2A
Synchronous Step Down Regulator
TITAN MICRO
/a85T
Functional Pin Description
Pin Name
Pin No.
(SOT-23-5)
Pin No.
(SOT-23-6)
EN
1
1
Enable Control.
this pin floating.
GND
2
2
Ground Pin.
LX
3
3
Power Switching Output.
and low side NMOS.
VIN
4
4
Power Supply Input Pin. Drive VIN pin by 2.5V to 5.5V voltage to power on the chip.
PG
--
5
Open Drain Power Good Output Pin.
FB
5
6
Voltage Feedback Input Pin. Connect FB and VOUT with a resistive voltage divider.
This IC senses feedback voltage via FB and regulates it at 0.6V.
Pin Function
Pull high to turn the IC on, and pull low to disable the IC.
Don’t leave
Connect an inductor to the drains of internal high side PMOS
Block Diagram
EN
PG
VIN
1MΩ
Power Good
Undervoltage
Lockout
Bias Supply
Enable
Control
Slope Compensation
90%
VREF
FB
Control Logic
Current Limit
Logic
COMP
EA
Control
and
Driver
Logic
1
X
LX
Compensation
VREF
Soft
Start
Oscillator
COMP
GND
Figure 3. Block Diagram of TD8002
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TD8002
High Efficiency 1MHz 2A
Synchronous Step Down Regulator
TITAN MICRO
/a85T
Absolute Maximum Ratings (Note 1)
● VIN to GND --------------------------------------------------------------------------------------------------- -0.3V to +6.5V
● LX to GND --------------------------------------------------------------------------------------------------- -0.3V to (VIN+0.3)
● EN, FB, PG to GND ---------------------------------------------------------------------------------------- -0.3V to VIN
● Package hermal
esistance, (θJA)
SOT-23-5 ------------------------------------------------------------------------------------------ +250ºC/W
SOT-23-6 ------------------------------------------------------------------------------------------ +250ºC/W
● Package hermal
esistance, (θJC)
SOT-23-5 ------------------------------------------------------------------------------------------ +130°C/W
SOT-23-6 ------------------------------------------------------------------------------------------ +110°C/W
● Maximum Junction Temperature (TJ) ------------------------------------------------------------------- +150°C
● Lead Temperature (Soldering, 10 sec.) ---------------------------------------------------------------- +260°C
● Storage Temperature (TSTG) ------------------------------------------------------------------------------ -65°C to +150℃
Note 1:Stresses beyond those listed under “Absolute Maximum
atings" may cause permanent damage to the device
Recommended Operating Conditions (Note 2)
● Supply Voltage (VIN) ---------------------------------------------------------------------------------------- +2.5V to +5.5V
● Junction Temperature Range ---------------------------------------------------------------------------- -40°C to +125°C
● Ambient Temperature Range ----------------------------------------------------------------------------- -40°C to +85°C
Note 2:The device is not guaranteed to function outside its operating conditions.
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TD8002
High Efficiency 1MHz 2A
Synchronous Step Down Regulator
TITAN MICRO
/a85T
Electrical Characteristics
(VIN=5V, TA=25°C, unless otherwise specified.)
Parameter
Input Voltage Range
Symbol
VIN
Shutdown Current
ISHDN
Quiescent Current
Iq
Reference Voltage
VREF
FB Input Leakage Current
P-Channel MOSFET On-Resistance
(Note 3)
N-Channel MOSFET On-Resistance
(Note 3)
Conditions
IFB
Min
Typ
2.5
EN=GND
0.1
VFB=0.65V, IOUT=0A
80
0.588
VFB=VIN
Max
Unit
5.5
V
1
μA
μA
0.6
0.612
V
0.01
1
µA
RDS(ON)
180
mΩ
RDS(ON)
100
mΩ
P-Channel Current Limit (Note 3)
ILIM
2.1
A
EN High-Level Input Voltage
VIH
1.5
V
EN Low-Level Input Voltage
VIL
Under Voltage Lockout Voltage
0.4
V
UVLO
2.4
V
UVLO Hysteresis
VHYS
0.2
V
Oscillation Frequency
FOSC
IOUT=500mA
0.8
Minimum On Time
50
Maximum Duty Cycle
PG Rising Threshold
PG Sink Current
1
100
1.2
MHz
ns
%
VPG (H)
VFB Rising
90
%
IPG
VPG=0.1V
1
mA
100
Ω
VOUT Discharge Resistance
Thermal Shutdown Temperature (Note 3)
TSD
150
°C
Internal Soft Start Time
TSS
1
ms
Note 3:Guarantee by design.
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TD8002
High Efficiency 1MHz 2A
Synchronous Step Down Regulator
TITAN MICRO
/a85T
95
100
90
95
Efficiency (%)
Efficiency (%)
Typical Performance Curves
85
80
75
90
85
80
VOUT=3.3V
VOUT=1.2V
70
75
VIN=3.3V
VIN=5V
65
VIN=4.2V
VIN=5V
70
0
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
1.8
0
2
0.2
0.4
0.6
Load Current (A)
Figure 4. Efficiency vs. Load Current
1
1.2
1.4
1.6
1.8
2
80
100
Figure 5. Efficiency vs. Load Current
612
1.2
609
1.15
606
1.1
Frequency (MHz)
Feedback Voltage (mV)
0.8
Load Current (A)
603
600
597
594
1.05
1
0.95
0.9
VIN=5V
IOUT=0.5A
591
VIN=5V
IOUT=0.5A
0.85
588
0.8
-40
-20
0
20
40
60
80
100
-40
Temperature (°C)
0
20
40
60
Temperature (°C)
Figure 6. Feedback Voltage vs. Temperature
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Figure 7. Frequency vs. Temperature
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TD8002
TITAN MICRO
High Efficiency 1MHz 2A
Synchronous Step Down Regulator
/a85T
Typical Performance Curves (Continued)
VIN=5V, VOUT=1.2 , C
μF, C
μF, L
1.8μH, TA=+25°C, unless otherwise noted.
IOUT=2A
IOUT=0A
VIN
VIN
5V/div.
5V/div.
VOUT 500mV/div.
VOUT 500mV/div.
IOUT
1A/div.
IOUT
1A/div.
VLX
2V/div.
VLX
2V/div.
4ms/div.
4ms/div.
Figure 8. Power On through VIN Waveform
Figure 9. Power On through VIN Waveform
IOUT=0A
IOUT=2A
VIN
5V/div.
VOUT
500mV/div.
IOUT
1A/div.
VLX
2V/div.
VIN
5V/div.
VOUT
500mV/div.
IOUT
1A/div.
VLX
2V/div.
100ms/div.
Figure 10. Power Off through VIN Waveform
100ms/div.
IOUT=0A
Figure 11. Power Off through VIN Waveform
IOUT=2A
VEN
5V/div.
VEN
5V/div.
VOUT
500mV/div.
VOUT
500mV/div.
IOUT
1A/div.
IOUT
1A/div.
VLX
2V/div.
VLX
2V/div.
400μs/div.
400μs/div.
Figure 12. Power On through EN Waveform
Figure 13. Power On through EN Waveform
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TD8002
TITAN MICRO
High Efficiency 1MHz 2A
Synchronous Step Down Regulator
/a85T
Typical Performance Curves (Continued)
VIN=5V, VOUT=1.2 , C
μF, C
μF, L1=1.8μH, TA=+25°C, unless otherwise noted.
IOUT=2A
IOUT=0A
VEN
5V/div.
VOUT
500mV/div.
IOUT
1A/div.
VLX
2V/div.
4ms/div.
Figure 14. Power Off through EN Waveform
5V/div.
VOUT
500mV/div.
IOUT
1A/div.
VLX
2V/div.
4ms/div.
Figure 15. Power Off through EN Waveform
IOUT=0A
IOUT=2A
VOUT
20mV/div.
ILX
200mA/div.
VLX
VEN
VOUT 10mV/div.
ILX
1A/div.
VLX
2V/div.
2V/div.
20ms/div
1μs/div
Figure 16. Steady State Waveform
Figure 17. Steady State Waveform
IOUT=0.2A to 2A
VOUT 100mV/div.
IOUT
1A/div.
200μs/div.
Figure 18. Load Transient Waveform
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TD8002
TITAN MICRO
High Efficiency 1MHz 2A
Synchronous Step Down Regulator
/a85T
Function Description
Short Circuit Protection
The TD8002 provides short circuit protection
function to prevent the device damaged from short
condition. When the short condition occurs and
the feedback voltage drops lower than 40% of the
regulation level, this will activate the latch protection
circuit. Then output will be forced shutdown to
prevent the inductor current runaway and to reduce
the power dissipation within the IC under true short
circuit conditions. Once the short condition is
removed, reset EN or VIN to restart IC.
The TD8002
is a high efficiency, internal
compensation and constant frequency current mode
step-down synchronous DC/DC converter. It has
integrated high-side (180mΩ, typ) and low-side
(100mΩ, typ) power switches, and provides 2A
continuous load current. It regulates input voltage
from 2.5V to 5.5V, and down to an output voltage as
low as 0.6V.
Control Loop
Slope compensated current mode PWM control
provides stable switching and cycle-by-cycle current
limit for superior load, line response, protection of the
internal main switch and synchronous rectifier. The
TD8002 switches at a constant frequency (1MHz)
and regulates the output voltage. During each cycle,
the PWM comparator modulates the power
transferred to the load by changing the inductor peak
current based on the feedback error voltage. During
normal operation, the main switch is turned on for a
certain time to ramp the inductor current at each
rising edge of the internal oscillator, and switched off
when the peak inductor current is above the error
voltage.
When the main switch is off, the
synchronous rectifier will be turned on immediately
and stay on until next cycle starts.
Over Current Protection
The TD8002 over current protection function is
implemented by using cycle-by-cycle current limit
architecture. The inductor current is monitored by
measuring the high-side MOSFET series sense
resistor voltage. When the load current increases,
the inductor current will also increase. When the
peak inductor current reaches the current limit
threshold, the output voltage will start to drop.
When the over current condition is removed, the
output voltage will return to the regulated value.
Enable
The TD8002 EN pin provides digital control to turn
on/off the regulator. When the voltage of EN
exceeds the threshold voltage, the regulator will start
the soft start function. If the EN pin voltage is below
the shutdown threshold voltage, the regulator will
turn into the shutdown mode and the shutdown
current will be smaller than μA. For auto start-up
operation, connect EN to VIN.
Over Temperature Protection
The TD8002 incorporates an over temperature
protection circuit to protect itself from overheating.
When the junction temperature exceeds the thermal
shutdown threshold temperature, the regulator will
be shutdown. And the hysteretic of the over
temperature protection is 30°C (typ).
PG Signal Output (SOT-23-6 Package Only)
Soft Start
The TD8002 employs internal soft start function to
reduce input inrush current during start up. The
internal soft start time will be 1ms.
PG pin is an open-drain output and requires a pull
up resistor. PG is actively held low in soft-start,
standby and shutdown. It is released when the
output voltage rises above 90% of nominal
regulation point.
Under Voltage Lockout
When the TD8002 is power on, the internal circuits
will be held inactive until VIN voltage exceeds the
UVLO threshold voltage. And the regulator will be
disabled when VIN is below the UVLO threshold
voltage. The hysteretic of the UVLO comparator is
200mV (typ).
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TD8002
High Efficiency 1MHz 2A
Synchronous Step Down Regulator
TITAN MICRO
/a85T
Application Information
Output Voltage Setting
The output voltage VOUT is set by using a resistive
divider from the output to FB. The FB pin regulated
voltage is 0.6V. Thus the output voltage is:
A low ESR capacitor is required to keep the noise
minimum.
Ceramic capacitors are better, but
tantalum or low ESR electrolytic capacitors may
also suffice.
Output Capacitor Selection
The output capacitor is used to keep the DC output
voltage and supply the load transient current.
When operating in constant current mode, the
output ripple is determined by four components:
Table 2 lists recommended values of R1 and R2 for
most used output voltage.
Table 2 Recommended Resistance Values
VOUT
R1
R2
3.3V
453kΩ
100kΩ
2.5V
316kΩ
100kΩ
1.8V
200kΩ
100kΩ
1.5V
150kΩ
100kΩ
1.2V
100kΩ
100kΩ
PPL
t
PPL
C
t
PPL
PPL ( SL)
t
S
S
t
t
The following figures show the form of the ripple
contributions.
VRIPPLE(ESR)(t)
Place resistors R1 and R2 close to FB pin to prevent
stray pickup.
+
VRIPPLE(ESL) (t)
Input Capacitor Selection
The use of the input capacitor is filtering the input
voltage ripple and the MOSFETS switching spike
voltage.
Because the input current to the
step-down converter is discontinuous, the input
capacitor is required to supply the current to the
converter to keep the DC input voltage. The
capacitor voltage rating should be 1.25 to 1.5 times
greater than the maximum input voltage. The input
capacitor ripple current RMS value is calculated as:
( MS)
(t)
+
VRIPPLE(C) (t)
(t)
+
VNOISE (t)
(t)
Where D is the duty cycle of the power MOSFET.
This function reaches the maximum value at D=0.5
and the equivalent RMS current is equal to IOUT/2.
The following diagram is the graphical representation
of above equation.
=
VRIPPLE(t)
IIN(RMS) (A)
1.2
2A
1
(t)
0.8
0.6
1A
0.4
0.5A
0.2
0
10 20 30 40 50 60 70 80 90
D (%)
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TD8002
High Efficiency 1MHz 2A
Synchronous Step Down Regulator
TITAN MICRO
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Application Information (Continued)
PPL ( S )
PPL ( SL)
PPL (C)
F
SC
That will lower ripple current and result in lower
output ripple voltage.
The Δ L is inductor
peak-to-peak ripple current:
S
L
SL
L SL
F
SC
L
F
SC
L
The following diagram is an example to graphically
represent Δ L equation.
L C
ΔIL (A)
Where FOSC is the switching frequency, L is the
inductance value, VIN is the input voltage, ESR is the
equivalent series resistance value of the output
capacitor, ESL is the equivalent series inductance
value of the output capacitor and the COUT is the
output capacitor.
Low ESR capacitors are preferred to use. Ceramic,
tantalum or low ESR electrolytic capacitors can be
used depending on the output ripple requirements.
When using the ceramic capacitors, the ESL
component is usually negligible.
It is important to use the proper method to eliminate
high frequency noise when measuring the output
ripple. The figure shows how to locate the probe
across the capacitor when measuring output ripple.
Remove the scope probe plastic jacket in order to
expose the ground at the tip of the probe. It gives a
very short connection from the probe ground to the
capacitor and eliminates noise.
0.9
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0
L=1.2μH
L=1.5μH
L=2.2μH
2.5
3
3.5
5
5.5
VOUT=1.2V, FOSC=1MHz
A good compromise value between size and
efficiency is to set the peak-to-peak inductor ripple
current Δ L equal to 30% of the maximum load
current. But setting the peak-to-peak inductor
ripple current Δ L between 20%~50% of the
maximum load current is also acceptable. Then
the inductance can be calculated with the following
equation:
Probe Ground
L
L
VOUT
4
4.5
VIN (V)
(MA )
F
SC
L
To guarantee sufficient output current, peak inductor
current must be lower than the high-side
MOSFET current limit. The peak inductor current
is shown as below:
GND
Ceramic Capacitor
P A
(MA )
L
Inductor Selection
The output inductor is used for storing energy and
filtering output ripple current. But the trade-off
condition often happens between maximum energy
storage and the physical size of the inductor. The
first consideration for selecting the output inductor is
to make sure that the inductance is large enough to
keep the converter in the continuous current mode.
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TD8002
High Efficiency 1MHz 2A
Synchronous Step Down Regulator
TITAN MICRO
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Application Information (Continued)
Feedforward Capacitor Selection
Internal compensation function allows users saving
time in design and saving cost by reducing the
number of external components. The use of a
feedforward capacitor C3 in the feedback network is
recommended to improve transient response or
higher phase margin.
PCB Layout Recommendation
he device’s performance and stability are
dramatically affected by PCB layout.
It is
recommended to follow these general guidelines
shown as below:
1. Place the input capacitors and output capacitors
as close to the device as possible. The traces
which connect to these capacitors should be as
short and wide as possible to minimize parasitic
inductance and resistance.
VOUT
C3
2. Place feedback resistors close to the FB pin.
3. Keep the sensitive signal (FB) away from the
switching signal (LX).
4. Multi-layer PCB design is recommended.
FB
R2
GND
For optimizing the feedforward capacitor, knowing
the cross frequency is the first thing. The cross
frequency (or the converter bandwidth) can be
determined by using a network analyzer. When
getting the cross frequency with no feedforward
capacitor identified, the value of feedforward
capacitor C3 can be calculated with the following
equation:
FC
L1
VIN
4
3
LX
PG
5
2
GND
FB
6
1
EN
R1
C3
C
VOUT
C2
C1
VIN
R3
R1
TD8002
R2
SS
Figure 19. Recommended Layout Diagram
Where FCROSS is the cross frequency.
To reduce transient ripple, the feedforward capacitor
value can be increased to push the cross frequency
to higher region.
Although this can improve
transient response, it also decreases phase margin
and causes more ringing. In the other hand, if more
phase margin is desired, the feedforward capacitor
value can be decreased to push the cross frequency
to lower region.
In general, the feedforward
capacitor range is between 10pF to 330pF.
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TD8002
High Efficiency 1MHz 2A
Synchronous Step Down Regulator
TITAN MICRO
Marking Information
/a85T
4
5
TD8002
DYWWZ
3
2
1
D: Internal Code(A-Z)
Y:Year(7-2017,6-2016...)
WW:Week(01-53)
Z:Internal Code(00-09)
(1)
4
5
TD8002
DYYWW
3
2
1
D: Internal Code(A-Z)
YY:Year(17-2017,16-2016...)
WW:Week(01-53)
(2)
4
5
TD8002
XXXY
1
3
2
XXX: Wafer's Lot No
Y: Internal Code
(3)
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TD8002
High Efficiency 1MHz 2A
Synchronous Step Down Regulator
TITAN MICRO
/a85T
Outline Information
SOT-23-5 Package (Unit: mm)
SYMBOLS
UNIT
A
DIMENSION IN MILLIMETER
MIN
MAX
0.90
1.45
A1
0.00
0.15
A2
0.90
1.30
B
0.30
0.50
D
2.80
3.00
3.00
E
2.60
E1
1.50
1.70
e
0.90
1.00
e1
1.80
2.00
L
0.30
0.60
Note:Followed From JEDEC MO-178-C.
Carrier Dimensions
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TITAN MICRO
TD8002
High Efficiency 1MHz 2A
Synchronous Step Down Regulator
/a85T
Outline Information (Continued)
SOT-23-6 Package (Unit: mm)
SYMBOLS
UNIT
A
DIMENSION IN MILLIMETER
MIN
MAX
0.90
1.45
A1
0.00
0.15
A2
0.90
1.30
B
0.30
0.50
D
2.80
3.00
E
2.60
3.00
E1
1.50
1.70
e
0.90
1.00
e1
1.80
2.00
L
0.30
0.60
Note:Followed From JEDEC MO-178-C.
Carrier Dimensions
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