MP2359

1.2A, 24V, 1.4MHz

Step-Down Converter in a TSOT23-6
The Future of Analog IC Technology

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DESCRIPTION FEATURES

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The MP2359 is a monolithic step-down switch • 1.2A Peak Output Current
mode converter with a built-in power MOSFET.

P2 S F
• 0.35Ω Internal Power MOSFET Switch
It achieves 1.2A peak output current over a • Stable with Low ESR Output Ceramic
wide input supply range with excellent load and Capacitors

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line regulation. Current mode operation • Up to 92% Efficiency
provides fast transient response and eases loop • 0.1μA Shutdown Mode

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stabilization. Fault condition protection includes • Fixed 1.4MHz Frequency
cycle-by-cycle current limiting and thermal • Thermal Shutdown

TO ES ND
shutdown.
• Cycle-by-Cycle Over Current Protection

1H
The MP2359 requires a minimum number of • Wide 4.5V to 24V Operating Input Range
readily available standard external components. • Output Adjustable from 0.81V to 15V

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The MP2359 is available in TSOT23-6 and • Available in TSOT23-6 and SOT23-6
SOT23-6 packages.
E Packages

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EVALUATION BOARD REFERENCE APPLICATIONS
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Board Number Dimensions • Distributed Power Systems
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EV2359DJ-00B 2.1”X x 1.9”Y x 0.4”Z • Battery Charger
EF EW M

• Pre-Regulator for Linear Regulators

• WLED Drivers
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M For MPS green status, please visit MPS website under Quality Assurance.
“MPS” and “The Future of Analog IC Technology” are Registered Trademarks of
Monolithic Power Systems, Inc.
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TYPICAL APPLICATION
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Efficiency vs
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Load Currents
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5 1
100
VIN IN BST VIN = 12V
90
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12V CB
10nF 80
6 VOUT 70
EFFICIENCY (%)

SW VIN = 24V
MP2359 3.3V @ 1.2A
N

D1 60
B230A 50
4 3 40
OFF ON EN FB
GND 30
2 20
10 VOUT = 5V
0
0.01 0.1 1 10
LOAD CURRENT (A)

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 MP2359 – 1.2A, 24V, 1.4MHz STEP-DOWN CONVERTER IN A TSOT23-6

ORDERING INFORMATION
Part Number Package Top Marking Free Air Temperature (TA)

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MP2359DJ* TSOT23-6 F8 -40°C to +85°C
MP2359DT** SOT23-6 J6 -40°C to +85°C

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*For Tape & Reel, add suffix –Z (eg. M2359DJ–Z);

P2 S F
For RoHS compliant packaging, add suffix –LF (eg. MP2359DJ–LF–Z)
**For Tape & Reel, add suffix –Z (eg. M2359DT–Z);
For RoHS compliant packaging, add suffix –LF (eg. MP2359DT–LF–Z)

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PACKAGE REFERENCE

E
TO ES ND

1H
TOP VIEW

BST 1 6 SW

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E

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GND 2 5 IN

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ER D M
FB 3 4 EN

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EF EW M O

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ABSOLUTE MAXIMUM RATINGS (1) (4)
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Thermal Resistance θJA θJC

Supply Voltage VIN ....................................... 26V
TSOT23-6.............................. 220 .... 110.. °C/W
VSW ............................................................... 27V
SOT23-6 ................................ 220 .... 110.. °C/W
VBS ....................................................... VSW + 6V
All Other Pins ..................................-0.3V to +6V
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Notes:
Continuous Power Dissipation (TA = +25°C) (2) 1) Exceeding these ratings may damage the device.
2) The maximum allowable power dissipation is a function of the
TSOT23-6 .............................................. 0.568W
R N

maximum junction temperature TJ(MAX), the junction-to-

SOT23-6 ................................................ 0.568W
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ambient thermal resistance θJA, and the ambient temperature

Junction Temperature ...............................150°C TA. The maximum allowable continuous power dissipation at
any ambient temperature is calculated by PD(MAX)=(TJ(MAX)-
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Lead Temperature ....................................260°C TA)/θJA. Exceeding the maximum allowable power dissipation
Storage Temperature............... -65°C to +150°C will cause excessive die temperature, and the regulator will go
into thermal shutdown. Internal thermal shutdown circuitry
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(3) protects the device from permanent damage.

Recommended Operating Conditions 3) The device function is not guaranteed outside of the
Supply Voltage VIN ...........................4.5V to 24V recommended operating conditions.
4) Measured on JESD51-7, 4-layer PCB..
Output Voltage VOUT .......................0.81V to 15V
Ambient Temperature ................ -40°C to +85°C
Max input current into the EN pin............. 300μA

MP2359 Rev. 1.21 www.MonolithicPower.com 2

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 MP2359 – 1.2A, 24V, 1.4MHz STEP-DOWN CONVERTER IN A TSOT23-6

ELECTRICAL CHARACTERISTICS
VIN = 12V, TA = +25°C, unless otherwise noted.

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Parameters Symbol Condition Min Typ Max Units
Feedback Voltage VFB 4.5V ≤ VIN ≤ 24V 0.790 0.810 0.830 V

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Feedback Current IFB VFB = 0.8V 0.1 μA
Switch-On Resistance (5) RDS(ON) 0.35 Ω

P2 S F
Switch Leakage VEN = 0V, VSW = 0V 10 μA
Current Limit (5) 1.8 A

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Oscillator Frequency fSW VFB = 0.6V 1.2 1.4 1.7 MHz
Fold-back Frequency VFB = 0V 460 kHz

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Maximum Duty Cycle VFB = 0.6V 87 %
Minimum On-Time (5) tON 100 ns

TO ES ND
Under Voltage Lockout Threshold Rising 2.5 2.8 3.1 V

1H
Under Voltage Lockout Threshold Hysteresis 150 mV

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EN Input Low Voltage 0.4 V
EN Input High Voltage 1.2 V
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VEN = 2V 2.1
EN Input Current μA
ER D M
VEN = 0V 0.1

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Supply Current (Shutdown) IS VEN = 0V 0.1 1.0 μA
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Supply Current (Quiescent) IQ VEN = 2V, VFB = 1V 0.8 1.0 mA

Thermal Shutdown (5) 150 °C
Note:
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M
5) Guaranteed by design.
EC

PIN FUNCTIONS
Pin # Name Description
R

Bootstrap. A capacitor is connected between SW and BS pins to form a floating supply across
1 BST the power switch driver. This capacitor is needed to drive the power switch’s gate above the
supply voltage.
R N
T

Ground. This pin is the voltage reference for the regulated output voltage. For this reason care
2 GND must be taken in its layout. This node should be placed outside of the D1 to C1 ground path to
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prevent switching current spikes from inducing voltage noise into the part.
Feedback. An external resistor divider from the output to GND, tapped to the FB pin sets the
output voltage. To prevent current limit run away during a short circuit fault condition, the
N

3 FB
frequency foldback comparator lowers the oscillator frequency when the FB voltage is below
250mV.
On/Off Control Input. Pull EN above 1.2V to turn the device on. For automatic enable, connect a
4 EN
100kΩ resistor between this pin and Vin pin.
Supply Voltage. The MP2359 operates from a +4.5V to +24V unregulated input. C1 is needed
5 IN
to prevent large voltage spikes from appearing at the input.
6 SW Switch Output.

MP2359 Rev. 1.21 www.MonolithicPower.com 3

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 MP2359 – 1.2A, 24V, 1.4MHz STEP-DOWN CONVERTER IN A TSOT23-6

TYPICAL PERFORMANCE CHARACTERISTICS

VIN = 12V, VOUT = 3.3V, L = 4.7µH, C1 = 10µF, C2 = 22µF, TA = +25ºC, unless otherwise noted.

R
Efficiency vs Efficiency vs
Load Current Load Current

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100 100
VIN = 12V
90 VIN = 18V 90

P2 S F
80 80
70
EFFICIENCY (%)

70

EFFICIENCY (%)
VIN = 24V
60 60
VIN = 24V

D
50 50
40 40

E
30 30
20 20

TO ES ND
10 VOUT = 2.5V 10 VOUT = 5V

1H
0 0
0.01 0.1 1 10 0.01 0.1 1 10
LOAD CURRENT ( A) LOAD CURRENT (A)

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E

33
G
ER D M
Feedback Voltage vs Switching Frequency vs
Die Temperature
I 0.820
Die Temperature
1.50
EF EW M

SWITCHING FREQUENCY (MHz)

0.818 1.48
FEEDBACK VOLTAGE (V)

0.816 1.46
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0.814 1.44
M
0.812 1.42
EC

0.810 1.40
0.808 1.38
0.806 1.36
0.804 1.34
R

0.802 1.32
0.800 1.30
-50 -25 0 25 50 75 100 125 150 -50 -25 0 25 50 75 100 125 150
R N

DIE TEMPERATURE (OC) DIE TEMPERATURE (OC)

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 MP2359 – 1.2A, 24V, 1.4MHz STEP-DOWN CONVERTER IN A TSOT23-6

TYPICAL PERFORMANCE CHARACTERISTICS (continued)

VIN = 12V, VOUT = 3.3V, L = 4.7µH, C1 = 10µF, C2 = 22µF, TA = +25ºC, unless otherwise noted.

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Current Limit vs Steady State Test
Duty Cycle

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IOUT = 0.5A
3.0

P2 S F
2.5 VOUT
VOUT 20mV/div.
CURRENT LIMIT (A)

AC Coupled
2.0
50mV/div.

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1.5 VSW
IL 10V/div.
1A/div.

E
1.0
IL
500mA/div.
0.5 ILOAD

TO ES ND
1A/div.

1H
0
0 20 40 60 80 100 400ns/div.
DUTY CYCLE (%)

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Short Circuit Entry Short Circuit Recovery Start-up through Enable
E

33
No Load

G
ER D M
VEN

I 5V/div.
EF EW M

VOUT VOUT
1V/div. 1V/div.
VOUT
1V/div.
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M VSW
IL 10V/div.
EC

1A/div. IL IL
1A/div. 500mA/div.
R
R N

Start-up through Enable Shut-down through Enable Shut-down through Enable

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IOUT = 1A Resistive Load No Load IOUT = 1A Resistive Load

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VEN VEN
VEN
5V/div. 5V/div.
VOUT 5V/div.
N

2V/div.

VOUT VOUT
1V/div. 2V/div.
VSW
VSW VSW
10V/div.
10V/div. 10V/div.

IL IL IL
1A/div. 1A/div. 1A/div.

MP2359 Rev. 1.21 www.MonolithicPower.com 5

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 MP2359 – 1.2A, 24V, 1.4MHz STEP-DOWN CONVERTER IN A TSOT23-6

OPERATION
The MP2359 is a current mode buck regulator. If the sum of the Current Sense Amplifier output

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That is, the EA output voltage is proportional to and the Slope Compensation signal does not
the peak inductor current. exceed the EA output for a whole cycle, then

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the falling edge of the CLK resets the Flip-Flop.
At the beginning of a cycle, M1 is off. The EA
output voltage is higher than the current sense The output of the Error Amplifier integrates the

P2 S F
amplifier output, and the current comparator’s voltage difference between the feedback and
output is low. The rising edge of the 1.4MHz the 0.81V bandgap reference. The polarity is
CLK signal sets the RS Flip-Flop. Its output such that a FB pin voltage lower than 0.81V

D
turns on M1 thus connecting the SW pin and increases the EA output voltage. Since the EA
inductor to the input supply. output voltage is proportional to the peak

E
inductor current, an increase in its voltage also
The increasing inductor current is sensed and
increases current delivered to the output.
amplified by the Current Sense Amplifier. Ramp

TO ES ND
compensation is summed to the Current Sense

1H
Amplifier output and compared to the Error
Amplifier output by the PWM Comparator.

N
When the sum of the Current Sense Amplifier
E
output and the Slope Compensation signal

33
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exceeds the EA output voltage, the RS Flip-
ER D M
Flop is reset and M1 is turned off. The external
Schottky rectifier diode (D1) conducts the
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inductor current.
EF EW M O

IN 5
M
CURRENT SENSE
AMPLIFIER
EC

x20 --
+

RAMP D
GENERATOR REGULATOR
BST
R

EN 4 REGULATOR OSCILLATOR
1.4MHz/460KHz S Q DRIVER M1
R N

+
T

-- R
R 6 SW
CURRENT
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1pF
LIMIT
COMPARATOR
REFERENCE 27pF
N

+
+EA
--
FB 3 -- PWM
ERROR COMPARATOR
AMPLIFIER
GND 2

Figure 1—Functional Block Diagram

MP2359 Rev. 1.21 www.MonolithicPower.com 6

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 MP2359 – 1.2A, 24V, 1.4MHz STEP-DOWN CONVERTER IN A TSOT23-6

APPLICATION INFORMATION
Setting Output Voltage Selecting the Input Capacitor
The external resistor divider is used to set the The input capacitor reduces the surge current

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output voltage (see the schematic on front drawn from the input supply and the switching
page). Table 1 shows a list of resistor selection noise from the device. The input capacitor

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for common output voltages. The feedback impedance at the switching frequency should be
resistor R1 also sets the feedback loop less than the input source impedance to prevent

P2 S F
bandwidth with the internal compensation high frequency switching current from passing
capacitor (see Figure 1). R2 can be determined through the input. Ceramic capacitors with X5R or
by: X7R dielectrics are highly recommended because

D
R1 of their low ESR and small temperature
R2 =
VOUT coefficients. For most applications, a 4.7µF
−1

E
0.81V capacitor is sufficient.

Table 1—Resistor Selection for Common Selecting the Output Capacitor

TO ES ND
Output Voltages The output capacitor keeps the output voltage

1H
ripple small and ensures feedback loop stability.
VOUT (V) R1 (kΩ) R2 (kΩ) The output capacitor impedance should be low

N
1.8 80.6 (1%) 64.9 (1%) at the switching frequency. Ceramic capacitors
E with X5R or X7R dielectrics are recommended

33
2.5 49.9 (1%) 23.7 (1%)

G
for their low ESR characteristics. For most
3.3 49.9 (1%) 16.2 (1%)
ER D M
applications, a 22µF ceramic capacitor will be
5 49.9 (1%) 9.53 (1%) sufficient.
I
EF EW M

Selecting the Inductor PCB Layout Guide

A 1µH to 10µH inductor with a DC current rating PCB layout is very important to achieve stable
of at least 25% percent higher than the operation. Please follow these guidelines and
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M
maximum load current is recommended for take Figure2 for references.
most applications. For highest efficiency, the 1) Keep the path of switching current short
EC

inductor’s DC resistance should be less than and minimize the loop area formed by Input
200mΩ. Refer to Table 2 for suggested surface cap, high-side MOSFET and schottky diode.
mount inductors. For most designs, the required
inductance value can be derived from the 2) Keep the connection of schottky diode
between SW pin and input power ground
R

following equation.
as short and wide as possible.
VOUT × ( VIN − VOUT )
L= 3) Ensure all feedback connections are short
R N

VIN × ΔIL × f SW
T

and direct. Place the feedback resistors

Where ΔIL is the inductor ripple current. and compensation components as close to
O

the chip as possible.

Choose the inductor ripple current to be 30% of
the maximum load current. The maximum 4) Route SW away from sensitive analog
N

inductor peak current is calculated from: areas such as FB.

ΔI L 5) Connect IN, SW, and especially GND
IL(MAX ) = ILOAD + respectively to a large copper area to cool
2
the chip to improve thermal performance
Under light load conditions below 100mA, a and long-term reliability. For single layer
larger inductance is recommended for improved PCB, exposed pad should not be soldered.
efficiency. See Table 2 for suggested inductors.
Also note that the maximum recommended load
current is 1A if the duty cycle exceeds 35%.

MP2359 Rev. 1.21 www.MonolithicPower.com 7

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 MP2359 – 1.2A, 24V, 1.4MHz STEP-DOWN CONVERTER IN A TSOT23-6

R2 R1 External Bootstrap Diode

An external bootstrap diode may enhance the
SGND efficiency of the regulator, the applicable

R
conditions of external BST diode are:

C3
3 FB EN 4

2 GND IN 5

1 BST SW 6
z VOUT=5V or 3.3V; and

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VOUT
z Duty cycle is high: D= >65%
VIN

P2 S F
L1 In these cases, an external BST diode is
R3

recommended from the output of the voltage

D
regulator to BST pin, as shown in Fig.3
External BST Diode
C1 IN4148

E
D1 C2 BST
CBST
PGND MP2359

TO ES ND

1H
SW 5V or 3.3V
L
COUT
Figure 2—PCB Layout

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Figure 3—Add Optional External Bootstrap
E

33
Diode to Enhance Efficiency

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The recommended external BST diode is
ER D M
IN4148, and the BST cap is 0.1~1µF.
I Table 2—Suggested Surface Mount Inductors
EF EW M

Current Dimensions
Manufacturer Part Number Inductance(µH) Max DCR(Ω) L x W x H (mm3)
Rating (A)
O

Toko
M A921CY-4R7M 4.7 0.027 1.66 6 x 6.3 x 3
Sumida CDRH4D28C/LD 4.7 0.036 1.5 5.1 x 5.1 x 3
EC

Wurth Electronics 7440530047 4.7 0.038 2.0 5.8 x 5.8 x 2.8

R
R N
T
O
N

MP2359 Rev. 1.21 www.MonolithicPower.com 8

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 MP2359 – 1.2A, 24V, 1.4MHz STEP-DOWN CONVERTER IN A TSOT23-6

TYPICAL APPLICATION CIRCUITS

D3

R
1N4148
(Optional)
5 1

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VIN IN BS

D2
C3 1N4148

P2 S F
22nF (Optional)
4 6 VOUT
OFF ON EN MP2359 SW
3.3V
D1

D
B230A-13-F
Notes:
1) D3 can be installed if VIN < 5V
3

E
2) D2 can be installed if VOUT < 5V FB
3) No need for both D2 and D3 GND
U1

TO ES ND

1H
N
Figure 4—1.4MHz, 3.3V Output at 1A Step-Down Converter
E

33
G
ER D M
5 1
VIN IN BST

I
6V-12V C3
10nF
EF EW M

6
SW
MP2359 D1
1N5819HW-7
O

LED1
M -VOUT -VOUT
4 3
OFF ON EN FB LED2
EC

GND
2
-VOUT LED3
-VOUT
R

Figure 5—White LED Driver Application

R N
T
O
N

MP2359 Rev. 1.21 www.MonolithicPower.com 9

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 MP2359 – 1.2A, 24V, 1.4MHz STEP-DOWN CONVERTER IN A TSOT23-6

PACKAGE INFORMATION
TSOT23-6

R
0.60 0.95

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2.80 TYP BSC
3.00

P2 S F
6 4
1.20
TYP
See Note 7

D
EXAMPLE

AAAA
TOP MARK
1.50 2.60 2.60

E
1.70 3.00 TYP
PIN 1

TO ES ND

1H
N
E 1 3

33
G
TOP VIEW RECOMMENDED LAND PATTERN
ER D M
I
EF EW M

0.84
1.00 MAX
O

0.90
M 0.09
SEATING PLANE 0.20
EC

0.30 0.00
0.95 BSC
0.50 0.10 SEE DETAIL "A"

FRONT VIEW SIDE VIEW

R

NOTE:
R N

1) ALL DIMENSIONS ARE IN MILLIMETERS.

T

GAUGE PLANE 2) PACKAGE LENGTH DOES NOT INCLUDE MOLD FLASH,

0.25 BSC PROTRUSION OR GATE BURR.
O

3) PACKAGE WIDTH DOES NOT INCLUDE INTERLEAD FLASH

OR PROTRUSION.
4) LEAD COPLANARITY (BOTTOM OF LEADS AFTER FORMING)
0.30 SHALL BE 0.10 MILLIMETERS MAX.
N

0o-8o 0.50 5) DRAWING CONFORMS TO JEDEC MO-193, VARIATION AB.

6) DRAWING IS NOT TO SCALE.
DETAIL “A” 7) PIN 1 IS LOWER LEFT PIN WHEN READING TOP MARK FROM
LEFT TO RIGHT, (SEE EXAMPLE TOP MARK)

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 MP2359 – 1.2A, 24V, 1.4MHz STEP-DOWN CONVERTER IN A TSOT23-6

SOT23-6
0.60 0.95

R
2.80 TYP BSC
3.00

O
6 4
1.20
TYP
See Note 7

P2 S F
EXAMPLE
TOP MARK

AAAA 1.50 2.60 2.60

D
1.70 3.00 TYP
PIN 1

E
TO ES ND
1

1H
3

N
TOP VIEW RECOMMENDED LAND PATTERN
E

33
G
ER D M
I
EF EW M

0.90
1.30 1.45 MAX

0.09
O

SEATING PLANE 0.20

M 0.30 0.00 SEE DETAIL "A"
0.95 BSC
0.50 0.15
EC

FRONT VIEW SIDE VIEW

NOTE:
R

1) ALL DIMENSIONS ARE IN MILLIMETERS.

GAUGE PLANE 2) PACKAGE LENGTH DOES NOT INCLUDE MOLD FLASH,
0.25 BSC PROTRUSION OR GATE BURR.
R N
T

3) PACKAGE WIDTH DOES NOT INCLUDE INTERLEAD FLASH

OR PROTRUSION.
4) LEAD COPLANARITY (BOTTOM OF LEADS AFTER FORMING)
O

0.30 SHALL BE 0.10 MILLIMETERS MAX.

0o-8o 0.55 5) DRAWING CONFORMS TO JEDEC MO-193, VARIATION AB.
6) DRAWING IS NOT TO SCALE.
N

DETAIL “A” 7) PIN 1 IS LOWER LEFT PIN WHEN READING TOP MARK FROM
LEFT TO RIGHT, (SEE EXAMPLE TOP MARK)

NOTICE: The information in this document is subject to change without notice. Please contact MPS for current specifications.
Users should warrant and guarantee that third party Intellectual Property rights are not infringed upon when integrating MPS
products into any application. MPS will not assume any legal responsibility for any said applications.

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