36V, 670kHz Step-up Converter with a 0.5A Switch
The Future of Analog IC Technology
DESCRIPTION
The MP3217 is a monolithic step up converter integrating a 0.5A, 0.6Ω internal switch. The MP3217 uses current mode, fixed frequency architecture to regulate the output voltage, providing fast transient response and cycle by cycle current limit.
The MP3217 includes under-voltage lockout, over voltage protection and thermal overload protection preventing damage in the event of an output overload.
The MP3217 is available in small 6-pin TSOT23 package. FEATURES
• Internal 0.6Ω Power MOSFET • Up to 36V Output Voltage
• 670kHz Fixed Switching Frequency • 42V Over Voltage Shutdown
• Cycle-by-Cycle Over Current Protection • UVLO, Thermal Shutdown
• Available in TSOT23-6 Packages
APPLICATIONS
• APD Bias Generation • Portable Applications
• Handheld Computers and PDAs • Digital Still Cameras
“Monolithic Power Systems”, “MPS”, and “The Future of Analog IC Technology” are Registered Trademarks of Monolithic Power Systems, Inc.
TYPICAL APPLICATION
D1B0540
OUTPUT CURRENT (mA)
Efficiency vs. Output Current
E F F I C I E N C Y (%)
ORDERING INFORMATION
* For Tape & Reel, add suffix –Z (e.g. MP3217DJ–Z);
For RoHS Compliant Packaging, add suffix –LF (e.g. MP3217DJ–LF–Z)
PACKAGE REFERENCE
ABSOLUTE MAXIMUM RATINGS (1)
SW Pin.........................................–0.5V to +44V All Other Pins..............................–0.3V to +6.5V
Continuous Power Dissipation (T A = +25°C) (2)
.......................................................... 0.56W Junction Temperature...............................150°C
Lead Temperature....................................260°C Storage Temperature..............–55°C to +150°C
Recommended Operating Conditions (3)
IN Supply Voltage..............................2.5V to 6V SW Pin................................................V IN to 36V Operating Temperature.............–40°C to +85°C Thermal Resistance
(4)
θJA
θJ C
TSOT23-6..............................220....110..°C/W Notes: 1) Exceeding these ratings may damage the device.
2) The maximum allowable power dissipation is a function of the
maximum junction temperature T J (MAX), the junction-to-ambient thermal resistance θJA , and the ambient temperature
T A . The maximum allowable continuous power dissipation at
any ambient temperature is calculated by P D (MAX)=(T J (MAX)-T A )/θJA . Exceeding the maximum allowable power dissipation will cause excessive die temperature, and the regulator will go into thermal shutdown. Internal thermal shutdown circuitry protects the device from permanent damage.
3) The device is not guaranteed to function outside of its
operating conditions.
4) Measured on JESD51-7, 4-layer PCB.
Part Number*
Package
Top Marking
Temperature
MP3217DJ TSOT23-6
7H -40°C to +85°C
V IN = V EN = 5V, T A = +25°C, unless otherwise noted.
Max Units
Typ Parameters Symbol
Condition Min Operating Input Voltage V IN 2.5 6 V
Supply Current (Shutdown) V EN = 0V 10 µA
Supply Current (Quiescent) V FB = 0.15V 460 560µA
Switching Frequency f SW570 670 770kHz
Maximum Duty Cycle V FB = 0V 92 %
Under Voltage Lockout
IN Under Voltage Lockout UVLO V IN Rising 2.25 2.45V
Under Voltage Lockout
92 mV Hysteresis
Over Voltage Shutdown
V OV V OV Rising 42 V Threshold
Enable
EN OFF Threshold V EN Falling 0.8 V
EN ON Threshold V EN Rising 2 V
Feedback
FB Voltage V FB 1.20 1.24 1.28V
FB Input Bias Current V FB = 1.2V -100 nA
Output Switch
SW On-Resistance (5)R ON 0.6 Ω
SW Current Limit (5)Duty Cycle = 60% 0.50 A
Thermal Shutdown (5)150
°C
Notes:
5) Guaranteed by design.
PIN FUNCTIONS
Pin #
Name
Pin Function
1 PGND Power Ground.
2 GND Ground.
3 FB
Feedback Input. Reference voltage is 1.24V,Connect a resistor divider from the output to this pin. 4 EN ON/OFF Control Input. A voltage greater than 2V will turn the part on and less than 0.8V will turn the part off. When not used, float EN to the input source for automatic startup. 5
IN
Input Supply Pin. Must be locally bypassed.
6 SW
Power Switch Output. SW is the drain of the internal MOSFET switch. Connect the
power inductor and output rectifier to SW.
TYPICAL PERFORMANCE CHARACTERISTICS
Circuit refer to Figure 2, V IN =5V, V OUT =33V, T A =+25˚C, unless otherwise noted.
OUTPUT CURRENT (mA)INPUT VOLTAGE (V)
OUTPUT CURRENT (mA)
Efficiency vs. Output Current
Line Regulation
I OUT =10mA
Load Regulation
E F F I C I E N C Y (%)
510152025
Current Limit vs. Duty
V FB =0V
100
2003004005006007008009001000
DUTY (%)
C U R R E N T L I M I T (m A )
4.54..74.84.95
5.15.25.35.45.5
V OUT /AC 20mV/div
V SW 20V/div I INDUCTOR 100mA/div
V OUT /AC 50mV/div
V SW 20V/div I INDUCTOR 100mA/div
2us/div
2us/div
Steady State
I OUT =0mA
Steady State
I OUT =10mA
V IN Power On
I OUT =10mA
V OUT 20V/div V IN 2V/div V SW 20V/div I INDUCTOR 200mA/div
1ms/div
L O A D R E G U L A T I O N (%)
-0.30
-0.20
-0.100.000.100.200.30
L I N E R E G U L A T I O N (%)
V OUT 20V/div V EN 5V/div V SW 20V/div I INDUCTOR 200mA/div
200us/div
2ms/div
V IN Power Off
I OUT =10mA
EN Power On
I OUT =10mA
V OUT 20V/div V IN 2V/div V SW 20V/div I INDUCTOR 200mA/div
102030405060708090100
-0.60
-0.40-0.200.000.200.400.60
TYPICAL PERFORMANCE CHARACTERISTICS (continued)
Circuit refer to Figure 2, V
IN
=5V, V OUT =33V, T A =+25˚C, unless otherwise noted.
V OUT 20V/div V EN 5V/div V SW 20V/div I INDUCTOR 200mA/div
V OUT 20V/div V EN 5V/div V SW 20V/div I INDUCTOR 200mA/div
V OUT 20V/div V EN 5V/div V SW 20V/div I INDUCTOR 200mA/div
200us/div
100us/div
100us/div
EN Power Off
I OUT =10mA
Over Voltage Protection
Start up without R1
Over Voltage Protection
Remove R1 at working
OPERATION
The MP3217 uses a constant frequency, peak current mode boost regulator architecture to regulate the output voltage. The operation of the MP3217 can be understood by referring to the block diagram of Figure 1.
At the start of each oscillator cycle the FET is turned on through the control circuitry. To prevent sub-harmonic oscillations at duty cycles greater than 50 percent, a stabilizing ramp is added to the output of the current sense amplifier and the result is fed into the positive input of the PWM comparator. When this voltage equals the output voltage of the error amplifier the power FET is turned off.
The voltage at the output of the error amplifier is an amplified version of the difference between the 1.24V reference voltage and the
feedback voltage. In this way the peak current level keeps the output in regulation.
If the feedback voltage starts to drop, the output of the error amplifier increases. This results in more current flowing through the power FET, thus increasing the power delivered to the output.
Over voltage protection shuts off the MP3217 if the output voltage goes too high. In some cases, loose high side resistor or improper divided resistor; this results in the feedback voltage is always below reference. The part runs at maximum duty cycle boosting the output voltage higher and higher. If the output ever exceeds 42V, the MP3217 shuts down. And It does not switch again until the power is
recycled.
SW
GND
FB
IN
Figure 1—Functional Block Diagram
APPLICATION INFORMATION
Components referenced below apply to
Typical Application Circuit refer to Figure 2. Setting the Output Voltage
Set the output voltage by selecting the resistive voltage divider ratio. Use 5.1k Ω for the low-side resistor R2 of the voltage divider. Determine the high-side resistor R1 by the equation:
OUT FB FB
R2(V V )R1V ×−=
Where, V OUT is the output voltage, V FB = 1.24V. For R2 = 5.1k Ω and V OUT = 33V, then
R1 = 130.6k Ω. There choose a 133k Ω standard 1% value.
Selecting the Input Capacitor
An input capacitor is required to supply the AC ripple current to the inductor, while limiting noise at the input source. This capacitor must have low ESR, so ceramic is the best choice. Use an input capacitor value of 4.7µF or greater. This capacitor must be placed physically close to the IN pin. Since it reduces the voltage ripple seen at IN, it also reduces the amount of EMI passed back along that line to the other circuitry.
Selecting the Output Capacitor The output capacitor is required to maintain the DC output voltage. Low ESR capacitors are preferred to keep the output voltage ripple to a minimum. The characteristic of the output capacitor also affects the stability of the regulation control system. Ceramic, tantalum, or low ESR electrolytic capacitors are recommended. In the case of ceramic capacitors, the impedance of the capacitor at the switching frequency is dominated by the capacitance, and so the output voltage ripple is mostly independent of the ESR. The output voltage ripple is estimated to be: IN LOAD
OUT RIPPLE
SW
V 1 -I V V C2f ⎛⎞
×⎜⎟⎝
⎠≈× Where V RIPPLE is the output ripple voltage, V IN and V OUT are the DC input and output voltages respectively, I LOAD is the load current, f SW is the switching frequency, and C2 is the capacitance of the output capacitor.
Selecting the Inductor
The inductor is required to force the higher output voltage while being driven by the lower input voltage. A larger value inductor results in less ripple current that results in lower peak inductor current, reducing stress on the internal power switch. However, the larger value inductor has a larger physical size, higher series resistance, and/or lower saturation current.
Inductance from 2.2µH to 33µH is a good choice for high efficiency and small size. To prevent saturation, use an inductor with a saturation current rating that is higher than the device current limit.
Selecting the Diode
The output rectifier diode supplies current to the inductor when the internal power MOSFET is off. To reduce losses due to diode forward voltage and recovery time, use a Schottky diode with the MP3217. The diode should be rated for a reverse voltage equal to or greater than the output voltage used. The average current rating must be greater than the maximum load current expected, and the peak current rating must be greater than the peak inductor current.
Layout Consideration High frequency switching regulators require very careful layout for stable operation and low noise. All components must be placed as close to the IC as possible. Keep the path between the SW pin, output diode, output capacitor and GND pin extremely short for minimal noise and ringing. The input capacitor must be placed close to the IN pin for best decoupling. All feedback components must be kept close to the FB pin to prevent noise injection on the FB pin trace. The ground return of the input and output capacitors should be tied close to the GND pin. See the MP3217 demo board layout for reference.
TYPICAL APPLICATION CIRCUIT
VIN
D15V
Bias
GND
EN VOUT
33V/10mA
GND
Figure 2—V IN =5V V OUT =33V I OUT =10mA Boost Circuit
Figure 3—V IN =3.3V V OUT =70V Voltage Doubler Circuit
NOTICE: The information in this document is subject to change without notice. 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.
PACKAGE INFORMATION
TSOT23-6
TOP VIEW FRONT VIEW SIDE VIEW
RECOMMENDED LAND PATTERN
NOTE:
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 AA.6) DRAWING IS NOT TO SCALE.
SEE DETAIL "A"
DETAIL “A”
