TS2508
2A / 330KHz PWM Buck Converter
1/8 Version: B07
SOP-8
General Description
TS2508 consists of step-down switching regulator with PWM control. These devise include a reference voltage
source, oscillation circuit, error amplifier, internal PMOS and etc. TS2508 provides low-ripple power, high efficiency,
and excellent transient characteristics. The PWM control circuit is able to very the duty ratio linearly form 0 up to
100%. This converter also contains an error amplifier circuit as well as a soft-start circuit that prevents overshoot at
startup. An enable function, an over current protect function and short circuit protect function are built inside, and
when OCP or SCP happens, the operation frequency will be reduced. Also, an internal compensation block is built in
to minimum external component count. With the addition of an internal P-channel Power MOS, a coil, capacitors, and
a diode connected externally, these ICs can function as step-down switching regulators. They serve as ideal power
supply units for portable devices when coupled with the SOP-8 package, providing such outstanding features as low
current consumption. Since this converter can accommodate an input voltage up to 20V, it is also suitable for the
operation via an AC adapter.
Ordering Information
Part No.
Packing
TS2508CS RL
2.5Kpcs / 13” Reel
Features
● Input Voltage: 3.6V~20V
● Output Voltage: 0.8V~Vcc
● Duty Ratio: 0%~100% PWM Control
● Oscillation Frequency: 330kHz typ.
● Soft-Start (SS), Current Limit (CL), Enable Function
● Thermal Shutdown Function
● Short Circuit Protect (SCP)
● Built-in Internal SW P-Channel MOSFET
Application
● Simple High-efficiency Step down Regulator
● On-Card Switching Regulators
Absolute Maximum Rating
Parameter
Symbol
Rating
Unit
VCC Pin Voltage
VCC
Gnd -0.3 to Gnd +22
V
Feedback Pin Voltage
VFB
Gnd -0.3 to VCC
V
ON/OFF Pin Voltage
VEN
Gnd -0.3 to VCC +0.3
V
Switch Pin Voltage
VSW
Gnd -0.3 to VCC +0.3
V
Power Dissipation
PD
Internally limited
mW
Storage Temperature Range
TST
-40 to +150
℃
Operating Temperature Range
TOP
-20 to +125
℃
Operating Supply Voltage
VOP
+3.6 to +20
V
Output Current
IO
2
A
Thermal Resistance from Junction to case
θJC
25
℃/W
Thermal Resistance from Junction to ambient
θJA
70
℃/W
Pin Definition:
1. FB
8. Vss
2. Enable
7. Vss
3. Ocset
6. SW
4. Vcc
5. SW
TS2508
2A / 330KHz PWM Buck Converter
2/8 Version: B07
Electrical Specifications (VIN=12V, Ta=25oC unless otherwise noted)
Characteristics
Symbol
Conditions
Min
Typ
Max
Units
Feedback Voltage
VFB
IOUT =0.1A
0.784
0.800
0.816
V
Quiescent Current
Iq
VFB =1.2V force driver off
--
3
5
mA
Feedback Bias Current
IFB
IOUT =0.1A
--
0.1
0.5
uA
Shutdown Supply Current
ISD
VEN =0V
--
2
10
uA
OCSET pin bias current
IOCSET
95
110
125
uA
Switch Current
ISW
2
--
--
A
Line Regulation
∆VOUT/VOUT
VCC = 5V~20V, IOUT =0.2A
--
1
2
%
Load Regulation
IOCSET
IOUT = 0.1 to 2A
--
0.3
0.5
%
Oscillation Frequency
FOSC
SW pin
260
330
400
KHz
VSH
High (regulator ON)
2.0
--
--
EN Pin Logic input
threshold voltage
VSL
Low (regulator OFF)
--
--
0.8
V
ISH
VEN =2.5V (ON)
--
20
--
uA
EN Pin Input Current
ISL
VEN =0.3V (OFF)
--
-10
--
uA
Soft-Start Time
TSS
0.3
4
8
ms
VCC = 5V, VFB = 0V
--
100
140
mΩ
Internal P-MOS RDSON
RDSON
VCC = 12V, VFB = 0V
--
70
100
mΩ
IOUT = 1A
--
92
--
Efficiency
EFFI
VCC = 12V,
VOUT = 5V
IOUT = 2A
--
92
--
%
Block Diagram
Pin Assignment
Name
Description
Name
Description
FB
Feedback pin
Vss
GND pin
EN
H:Normal operation (Step-down)
L:Step-down operation stopped (All circuit deactivated)
Vss
GND pin
OCSET
Add an external resistor to set max switch output
current.
SW
Switch pin. Connect external inductor
& diode here
Vcc
IC power supply pin
SW
Switch pin. Connect external inductor
& diode here
TS2508
2A / 330KHz PWM Buck Converter
3/8 Version: B07
Application Circuit
Typical Circuit
L1 recommend value (VIN=12V, IOUT=2A )
VOUT
1.8V
2.5V
3.3V
5V
L1 Value
18uH
22uH
27uH
33uH
Function Descriptions
PWM Control
The TS2508 consists of DC/DC converters that employ a pulse-width modulation (PWM) system. In converters of the
TS2508, the pulse width varies in a range from 0 to 100%, according to the load current. The ripple voltage produced
by the switching can easily be removed through a filter because the switching frequency remains constant. Therefore,
these converters provide a low-ripple power over broad ranges of input voltage and load current.
RDS(ON) Current Limiting
The current limit threshold is setting by the external resistor (R3) connecting from VCC supply to OCSET pin. The
internal 110uA sink current crossing the resistor sets the voltage at pin of OCSET. When the PWM voltage is less than
the voltage at OCSET, an over-current condition is triggered. Please refer to the formula for setting the minimum
current limit value:
(Normally, The ISW(MAX) setting more than IOUT 1.2A)
Example: ISW=(0.11mA * 2k + 0.08) / 70mΩ = 3.2A – (VIN=12V)
ISW=(0.11mA * 3.3k + 0.08) / 1000mΩ = 3.5A – (VIN=5V)
TS2508
2A / 330KHz PWM Buck Converter
4/8 Version: B07
Function Descriptions (Continue)
Setting the Output Voltage
Application circuit item shows the basic application circuit with TS2508 adjustable output version. The external resistor
sets the output voltage according to the following equation:
Table 1: Resistor select for output voltage setting
VOUT
R2
R1
1.3K
6.8K
5V
5.6K
30K
1.5K
4.7K
3.3V
5.6K
18K
2.2K
4.7K
2.5V
5.6K
12K
1.8V
1.2K
1.5K
1.5V
2.2K
2K
1.2V
2K
1K
1V
2K
0.5K
The R2 setting 5.6k that no load current can be reduce to under 4mA for EL CAP
Input Capacitor Selection
This capacitor should be located close to the IC using short leads and the voltage rating should be approximately 1.5
times the maximum input voltage. The RMS current rating requirement for the input capacitor of a buck regulator is
approximately 1⁄2 the DC load current. A low ESR input capacitor sized for maximum RMS current must be used. A
220µF low ESR capacitor for most applications is sufficient
Output Capacitor Selection
The output capacitor is required to filter the output and provide regulator loop stability. The important capacitor
parameters are; the 100KHz Equivalent Series Resistance (ESR), the RMS ripples current rating, voltage rating, and
capacitance value. For the output capacitor, the ESR value is the most important parameter. The ESR can be
calculated from the following formula.
VRIPPLE = ∆IL x ESR = 0.33A x 130mΩ = 43mV
An aluminum electrolytic capacitor's ESR value is related to the capacitance and its voltage rating. In most case, higher
voltage electrolytic capacitors have lower ESR values. Most of the time, capacitors with much higher voltage ratings
may be needed to provide the low ESR values required for low output ripple voltage. It is recommended to replace this
low ESR capacitor by using a 330µF low ESR values < 130mΩ
Inductor Selection
For most designs, the operate with inductors of 12µH to 33µH. The inductor value can be derived from the following
equation:
Where is inductor Ripple Current. Large value inductors lower ripple current and small value inductors result in high
ripple currents. Choose inductor ripple current approximately 15% of the maximum load current 2A, ∆IL=0.3A. The DC
current rating of the inductor should be at least equal to the maximum load current plus half the ripple current to
prevent core saturation (2A+0.15A).
TS2508
2A / 330KHz PWM Buck Converter
5/8 Version: B07
Function Descriptions (Continue)
Layout Guidance
If you need low Tc & Tj or large PD (Power Dissipation), The dual SW pins (5&6) and Gnd pins (7&8) on the SOP-8
package are internally connected to die pad, The PCB layout should allow for maximum possible copper area at the
SW pins.
1. Connect C3 to VCC and Gnd pin as closely as possible to get good power filter effect.
2. Connect R3 to VCC and OCSET pin as closely as possible.
3. Connect ground side of the C2 & D1 as closely as possible.
Electrical Characteristics Curve
Figure 1. Feedback Voltage vs. Input Voltage
Figure 2.Quiescent Current vs. Input Voltage
Figure 3. Frequency vs. Input Voltage
Figure 4. Frequency vs. Temperature
TS2508
2A / 330KHz PWM Buck Converter
6/8 Version: B07
Electrical Characteristics Curve
Figure 7. Feedback Voltage vs. Temperature
Figure 8. Quiescent Current vs. Temperature
Figure 9. Efficiency vs. Output Current
Figure 10. Efficiency vs. Output Current
TS2508
2A / 330KHz PWM Buck Converter
7/8 Version: B07
SOP-8 Mechanical Drawing
Marking Diagram
Y
= Year Code
M
= Month Code
(A=Jan, B=Feb, C=Mar, D=Apl, E=May, F=Jun, G=Jul, H=Aug, I=Sep,
J=Oct, K=Nov, L=Dec)
L
= Lot Code
SOP-8 DIMENSION
MILLIMETERS
INCHES
DIM
MIN
MAX
MIN
MAX.
A
4.80
5.00
0.189
0.196
B
3.80
4.00
0.150
0.157
C
1.35
1.75
0.054
0.068
D
0.35
0.49
0.014
0.019
F
0.40
1.25
0.016
0.049
G
1.27BSC
0.05BSC
K
0.10
0.25
0.004
0.009
M
0º
7º
0º
7º
P
5.80
6.20
0.229
0.244
R
0.25
0.50
0.010
0.019
TS2508
2A / 330KHz PWM Buck Converter
8/8 Version: B07
Notice
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assumes no responsibility or liability for any errors or inaccuracies.
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