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TM
MP2359
1.2A, 24V, 1.4MHz Step-Down Converter in a TSOT23-6
The Future of Analog IC Technology
TM
DESCRIPTION
The MP2359 is a monolithic step-down switch mode converter with a built-in power MOSFET. It achieves 1.2A peak output current over a wide input supply range with excellent load and line regulation. Current mode operation provides fast transient response and eases loop stabilization. Fault condition protection includes cycle-by-cycle current limiting and thermal shutdown. The MP2359 requires a minimum number of readily available standard external components. The MP2359 is available in TSOT23-6 and SOT23-6 packages.
FEATURES
* * * * * * * * * * * 1.2A Peak Output Current 0.35 Internal Power MOSFET Switch Stable with Low ESR Output Ceramic Capacitors Up to 92% Efficiency 0.1A Shutdown Mode Fixed 1.4MHz Frequency Thermal Shutdown Cycle-by-Cycle Over Current Protection Wide 4.5V to 24V Operating Input Range Output Adjustable from 0.81V to 15V Available in TSOT23-6 and SOT23-6 Packages Distributed Power Systems Battery Charger Pre-Regulator for Linear Regulators WLED Drivers
EVALUATION BOARD REFERENCE
Board Number EV2359DJ-00B Dimensions 2.1"X x 1.9"Y x 0.4"Z
APPLICATIONS
* * * *
"MPS" and "The Future of Analog IC Technology" are Trademarks of Monolithic Power Systems, Inc.
TYPICAL APPLICATION
Efficiency vs Load Currents
12V
VIN
5
IN
BST
1
100
CB 10nF
90 80
VIN = 12V
MP2359
OFF ON
4 EN
SW
EFFICIENCY (%)
6
D1 B230A
FB 3
VOUT 3.3V @ 1.2A
70 60 50 40 30 20 10 0 0.01
VIN = 24V
GND 2
VOUT = 5V 0.1 1 LOAD CURRENT (A) 10
MP2359 Rev. 1.1 6/23/2006
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TM
MP2359 - 1.2A, 24V, 1.4MHz STEP-DOWN CONVERTER IN A TSOT23-6
PACKAGE REFERENCE
ABSOLUTE MAXIMUM RATINGS (1)
Supply Voltage VIN ....................................... 26V VSW....................................... -0.3V to VIN + 0.3V VBS ....................................................... VSW + 6V All Other Pins................................. -0.3V to +6V Junction Temperature...............................150C Lead Temperature ....................................260C Storage Temperature ..............-65C to +150C
TOP VIEW BST GND FB 1 2 3 6 5 4 SW IN EN
Recommended Operating Conditions
(2)
Supply Voltage VIN ........................... 4.5V to 24V Output Voltage VOUT ...................... 0.81V to 15V Ambient Temperature ................-40C to +85C
Thermal Resistance
Part Number* MP2359DJ MP2359DT * Package TSOT23-6 SOT23-6 Temperature -40C to +85C -40C to +85C
(3)
TSOT23-6.............................. 220 .... 110.. C/W SOT23-6 ................................ 220 .... 110.. C/W
Notes: 1) Exceeding these ratings may damage the device. 2) The device function is not guaranteed outside of the recommended operating conditions. 3) Measured on approximately 1" square of 1 oz copper.
JA
JC
For Tape & Reel, add suffix -Z (eg. MP2359DJ-Z) For RoHS compliant packaging, add suffix -LF (eg. MP2359DJ-LF-Z)
ELECTRICAL CHARACTERISTICS
VIN = 12V, TA = +25C, unless otherwise noted.
Parameters Feedback Voltage Feedback Current Switch-On Resistance (4) Switch Leakage Current Limit (4) Oscillator Frequency Fold-back Frequency Maximum Duty Cycle Minimum On-Time (4) Under Voltage Lockout Threshold Rising Under Voltage Lockout Threshold Hysteresis EN Input Low Voltage EN Input High Voltage EN Input Current Supply Current (Shutdown) Supply Current (Quiescent) Thermal Shutdown (4)
Note: 4) Guaranteed by design.
Symbol Condition VFB IFB RDS(ON) VEN = 0V, VSW = 0V fSW VFB = 0.6V VFB = 0V VFB = 0.6V 4.5V VIN 24V VFB = 0.8V
Min 0.790
Typ 0.810 0.1 0.35
Max 0.830
Units V A A A MHz KHz % ns V mV V V A
10 1.2 1.8 1.4 460 87 100 2.8 150 1.7
tON 2.5
3.1 0.4
1.2 VEN = 2V VEN = 0V VEN = 0V VEN = 2V, VFB = 1V 2.1 0.1 0.1 0.8 150
IS IQ
1.0 1.0
A mA C
MP2359 Rev. 1.1 6/23/2006
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TM
MP2359 - 1.2A, 24V, 1.4MHz STEP-DOWN CONVERTER IN A TSOT23-6
PIN FUNCTIONS
Pin # 1 Name Description BST Bootstrap. A capacitor is connected between SW and BS pins to form a floating supply across the power switch driver. This capacitor is needed to drive the power switch's gate above the supply voltage. Ground. This pin is the voltage reference for the regulated output voltage. For this reason care must be taken in its layout. This node should be placed outside of the D1 to C1 ground path to 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 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. Supply Voltage. The MP2359 operates from a +4.5V to +24V unregulated input. C1 is needed to prevent large voltage spikes from appearing at the input. Switch Output.
2
GND
3 4 5 6
FB EN IN SW
TYPICAL PERFORMANCE CHARACTERISTICS
VIN = 12V, VOUT = 3.3V, L = 4.7H, C1 = 10F, C2 = 22F, TA = +25C, unless otherwise noted.
100 90 80
Efficiency vs Load Current
VIN = 18V
100 90 80
Efficiency vs Load Current
VIN = 12V
EFFICIENCY (%)
EFFICIENCY (%)
70 60 50 40 30 20 10 0 0.01 VOUT = 2.5V 0.1 1 LOAD CURRENT ( A) 10 VIN = 24V
70 60 50 40 30 20 10 0 0.01
VIN = 24V
VOUT = 5V 0.1 1 LOAD CURRENT (A) 10
Feedback Voltage vs Die Temperature
0.818
Switching Frequency vs Die Temperature
SWITCHING FREQUENCY (MHz)
1.50 1.48 1.46 1.44 1.42 1.40 1.38 1.36 1.34 1.32 1.30 -50 -25 0 25 50 75 100 125 150 DIE TEMPERATURE (OC)
0.820
FEEDBACK VOLTAGE (V)
0.816 0.814 0.812 0.810 0.808 0.806 0.804 0.802 0.800 -50 -25 0 25 50 75 100 125 150 DIE TEMPERATURE (OC)
MP2359 Rev. 1.1 6/23/2006
www.MonolithicPower.com MPS Proprietary Information. Unauthorized Photocopy and Duplication Prohibited. (c) 2006 MPS. All Rights Reserved.
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TM
MP2359 - 1.2A, 24V, 1.4MHz STEP-DOWN CONVERTER IN A TSOT23-6
TYPICAL PERFORMANCE CHARACTERISTICS (continued)
VIN = 12V, VOUT = 3.3V, L = 4.7H, C1 = 10F, C2 = 22F, TA = +25C, unless otherwise noted.
Current Limit vs Duty Cycle
3.0 2.5
VOUT 20mV/div.
Steady State Test
IOUT = 0.5A
CURRENT LIMIT (A)
2.0 1.5 1.0 0.5 0 0 20 40 60 80 DUTY CYCLE (%)
VOUT AC Coupled 50mV/div.
IL 1A/div. ILOAD 1A/div.
VSW 10V/div. IL 500mA/div.
100
400ns/div.
Short Circuit Entry
Short Circuit Recovery
Start-up through Enable
No Load
VEN 5V/div. VOUT 1V/div. VOUT 1V/div.
VOUT 1V/div. VSW 10V/div. IL 500mA/div.
IL 1A/div.
IL 1A/div.
Start-up through Enable
IOUT = 1A Resistive Load
VEN 5V/div. VEN 5V/div. VOUT 2V/div.
Shut-down through Enable
No Load
Shut-down through Enable
IOUT = 1A Resistive Load
VEN 5V/div.
VOUT 1V/div. VSW 10V/div. IL 1A/div. VSW 10V/div. IL 1A/div.
VOUT 2V/div. VSW 10V/div. IL 1A/div.
MP2359 Rev. 1.1 6/23/2006
www.MonolithicPower.com MPS Proprietary Information. Unauthorized Photocopy and Duplication Prohibited. (c) 2006 MPS. All Rights Reserved.
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TM
MP2359 - 1.2A, 24V, 1.4MHz STEP-DOWN CONVERTER IN A TSOT23-6
OPERATION
The MP2359 is a current mode buck regulator. That is, the EA output voltage is proportional to the peak inductor current. At the beginning of a cycle, M1 is off. The EA output voltage is higher than the current sense amplifier output, and the current comparator's output is low. The rising edge of the 1.4MHz CLK signal sets the RS Flip-Flop. Its output turns on M1 thus connecting the SW pin and inductor to the input supply. The increasing inductor current is sensed and amplified by the Current Sense Amplifier. Ramp compensation is summed to the Current Sense Amplifier output and compared to the Error Amplifier output by the PWM Comparator. When the sum of the Current Sense Amplifier output and the Slope Compensation signal exceeds the EA output voltage, the RS FlipFlop is reset and M1 is turned off. The external Schottky rectifier diode (D1) conducts the inductor current. If the sum of the Current Sense Amplifier output and the Slope Compensation signal does not exceed the EA output for a whole cycle, then the falling edge of the CLK resets the Flip-Flop. The output of the Error Amplifier integrates the voltage difference between the feedback and the 0.81V bandgap reference. The polarity is such that a FB pin voltage lower than 0.81V increases the EA output voltage. Since the EA output voltage is proportional to the peak inductor current, an increase in its voltage also increases current delivered to the output.
IN 5 + -D
REGULATOR
x20
RAMP GENERATOR
CURRENT SENSE AMPLIFIER
1 EN 4
REGULATOR OSCILLATOR 1.4MHz/460KHz
BST
S + -1pF
CURRENT LIMIT COMPARATOR
Q
DRIVER
M1 6 SW
R R
REFERENCE
27pF +EA -+ --
FB 3 GND 2
ERROR AMPLIFIER
PWM COMPARATOR
Figure 1--Functional Block Diagram
MP2359 Rev. 1.1 6/23/2006
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TM
MP2359 - 1.2A, 24V, 1.4MHz STEP-DOWN CONVERTER IN A TSOT23-6
APPLICATION INFORMATION
Setting Output Voltage The external resistor divider is used to set the output voltage (see the schematic on front page). Table 1 shows a list of resistor selection for common output voltages. The feedback resistor R1 also sets the feedback loop bandwidth with the internal compensation capacitor (see Figure 1). R2 can be determined by:
R2 = R1 VOUT -1 0.81V
Selecting the Input Capacitor The input capacitor reduces the surge current drawn from the input supply and the switching noise from the device. The input capacitor impedance at the switching frequency should be less than the input source impedance to prevent high frequency switching current from passing through the input. Ceramic capacitors with X5R or X7R dielectrics are highly recommended because of their low ESR and small temperature coefficients. For most applications, a 4.7F capacitor is sufficient. Selecting the Output Capacitor The output capacitor keeps the output voltage ripple small and ensures feedback loop stability. The output capacitor impedance should be low at the switching frequency. Ceramic capacitors with X5R or X7R dielectrics are recommended for their low ESR characteristics. For most applications, a 22F ceramic capacitor will be sufficient. PC Board Layout The high current paths (GND, IN and SW) should be placed very close to the device with short, direct and wide traces. The input capacitor needs to be as close as possible to the IN and GND pins. The external feedback resistors should be placed next to the FB pin. Keep the switch node traces short and away from the feedback network. External Bootstrap Diode It is recommended that an external bootstrap diode be added when the input voltage is no greater than 5V or the 5V rail is available in the system. This helps improve the efficiency of the regulator. The bootstrap diode can be a low cost one such as IN4148 or BAT54.
5V (External) or VIN (4.5V to 5V)
Table 1--Resistor Selection for Common Output Voltages
VOUT (V) 1.8 2.5 3.3 5 R1 (k) 80.6 (1%) 49.9 (1%) 49.9 (1%) 49.9 (1%) R2 (k) 64.9 (1%) 23.7 (1%) 16.2 (1%) 9.53 (1%)
Selecting the Inductor A 1H to 10H inductor with a DC current rating of at least 25% percent higher than the maximum load current is recommended for most applications. For highest efficiency, the inductor's DC resistance should be less than 200m. Refer to Table 2 for suggested surface mount inductors. For most designs, the required inductance value can be derived from the following equation.
L= VOUT x ( VIN - VOUT ) VIN x IL x f SW
Where IL is the inductor ripple current. Choose the inductor ripple current to be 30% of the maximum load current. The maximum inductor peak current is calculated from:
IL(MAX ) = ILOAD + I L 2
BS
MP2359
SW
10nF
Under light load conditions below 100mA, a larger inductance is recommended for improved efficiency. See Table 2 for suggested inductors. Also note that the maximum recommended load current is 1A if the duty cycle exceeds 35%.
Figure 2--External Bootstrap Diode This diode is also recommended for high duty cycle operation (when
VOUT >65%) applications. VIN
MP2359 Rev. 1.1 6/23/2006
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TM
MP2359 - 1.2A, 24V, 1.4MHz STEP-DOWN CONVERTER IN A TSOT23-6 Table 2--Suggested Surface Mount Inductors
Manufacturer Toko Sumida Wurth Electronics
Part Number A921CY-4R7M CDRH4D28C/LD 7440530047
Inductance(H) 4.7 4.7 4.7
Max DCR() 0.027 0.036 0.038
Current Rating (A) 1.66 1.5 2.0
Dimensions L x W x H (mm3) 6 x 6.3 x 3 5.1 x 5.1 x 3 5.8 x 5.8 x 2.8
TYPICAL APPLICATION CIRCUITS
D3 1N4148 (Optional) VIN
5 IN BS 1
C3 22nF OFF ON Notes: 1) D3 can be installed if VIN < 5V 2) D2 can be installed if VOUT < 5V 3) No need for both D2 and D3
4 EN
D2 1N4148 (Optional) VOUT 3.3V
MP2359
SW
6
D1 B230A-13-F
3
GND
FB
U1
Figure 3--1.4MHz, 3.3V Output at 1A Step-Down Converter
VIN 6V-12V
5
IN
BST
1
C3 10nF
MP2359
OFF ON
4 EN
SW
6
D1 1N5819HW-7
-VOUT -VOUT 3
LED1 LED2 LED3
GND 2
FB
-VOUT -VOUT
Figure 4--White LED Driver Application
MP2359 Rev. 1.1 6/23/2006
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TM
MP2359 - 1.2A, 24V, 1.4MHz STEP-DOWN CONVERTER IN A TSOT23-6
PACKAGE INFORMATION
TSOT23-6
2.80 3.00 6 4 0.60 TYP 0.95 BSC
1.20 TYP
See Note 7 EXAMPLE TOP MARK
PIN 1
AAAA
1 3
1.50 1.70
2.60 3.00
2.60 TYP
TOP VIEW
RECOMMENDED LAND PATTERN
0.84 0.90
1.00 MAX SEATING PLANE 0.30 0.50 0.95 BSC 0.00 0.10 SEE DETAIL "A" 0.09 0.20
FRONT VIEW
SIDE VIEW
NOTE:
GAUGE PLANE 0.25 BSC 1) ALL DIMENSIONS ARE IN MILLIMETERS. 2) PACKAGE LENGTH DOES NOT INCLUDE MOLD FLASH, PROTRUSION OR GATE BURR. 3) PACKAGE WIDTH DOES NOT INCLUDE INTERLEAD FLASH OR PROTRUSION. 4) LEAD COPLANARITY (BOTTOM OF LEADS AFTER FORMING) SHALL BE 0.10 MILLIMETERS MAX. 5) DRAWING CONFORMS TO JEDEC MO-193, VARIATION AB. 6) DRAWING IS NOT TO SCALE. 7) PIN 1 IS LOWER LEFT PIN WHEN READING TOP MARK FROM LEFT TO RIGHT, (SEE EXAMPLE TOP MARK)
0o-8o
0.30 0.50
DETAIL "A"
MP2359 Rev. 1.1 6/23/2006
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TM
MP2359 - 1.2A, 24V, 1.4MHz STEP-DOWN CONVERTER IN A TSOT23-6
SOT23-6
2.80 3.00 6 See Note 7 EXAMPLE TOP MARK 4 0.60 TYP 0.95 BSC
1.20 TYP
PIN 1
AAAA
1 3
1.50 1.70
2.60 3.00
2.60 TYP
TOP VIEW
RECOMMENDED LAND PATTERN
0.90 1.30
1.45 MAX SEATING PLANE 0.30 0.50 0.95 BSC 0.00 0.15 SEE DETAIL "A" 0.09 0.20
FRONT VIEW
SIDE VIEW
NOTE:
GAUGE PLANE 0.25 BSC 1) ALL DIMENSIONS ARE IN MILLIMETERS. 2) PACKAGE LENGTH DOES NOT INCLUDE MOLD FLASH, PROTRUSION OR GATE BURR. 3) PACKAGE WIDTH DOES NOT INCLUDE INTERLEAD FLASH OR PROTRUSION. 4) LEAD COPLANARITY (BOTTOM OF LEADS AFTER FORMING) SHALL BE 0.10 MILLIMETERS MAX. 5) DRAWING CONFORMS TO JEDEC MO-193, VARIATION AB. 6) DRAWING IS NOT TO SCALE. 7) PIN 1 IS LOWER LEFT PIN WHEN READING TOP MARK FROM LEFT TO RIGHT, (SEE EXAMPLE TOP MARK)
0o-8o
0.30 0.55
DETAIL "A"
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.
MP2359 Rev. 1.1 6/23/2006 www.MonolithicPower.com MPS Proprietary Information. Unauthorized Photocopy and Duplication Prohibited. (c) 2006 MPS. All Rights Reserved.
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