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EUP2624 620kHz/1.25MHz Step-up DC/DC Converter
DESCRIPTION
The EUP2624 is a high performance current mode, PWM step-up converter with pin selectable operating frequency. With an internal 2.1A, 170m[ MOSFET, it can generate 12V at up to 500mA output current from a 5V supply. The selectable 620kHz and 1.25MHz allows smaller inductors and faster transient response. An external compensation pin gives the user greater flexibility in setting loop compensation allowing the use of low ESR Ceramic output capacitors. Soft-start is controlled with an external capacitor, which determines the input current ramp rate during start-up. When shut down, it drawsO 10A of current and can operate down to 2.5V input supply. These features along with 1.25MHz switching frequency makes it an ideal device for portable equipment and TFT-LCD displays. The EUP2624 is available in an 8-pin MSOP package. The device is specified for operation over the full -40C to +85C temperature range.
FEATURES
90% Efficiency 2.1A, 170m Power MOSFET 2.5V to 5.5V Input Range Adjustable Output Voltage up to 28V 620kHz/1.25MHz Switching Frequency Selection Adjustable Soft-Start Internal Thermal Protection Small MSOP-8 package RoHS Compliant and 100% Lead (Pb)-Free
APPLICATIONS
TFT-LCD Displays DSL Modems Set-Top Boxes PCMCIA Cards Portable Equipment Handheld Devices
Typical Application Circuit
Figure 1. 5V to 12V Step-Up
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EUP2624
Figure 2. Triple Output TFT LCD Power Supply
Pin Configurations
Part Number Pin Configurations
EUP2624 MSOP-8
Pin Description
PIN COMP FB PIN 1 2 DESCRIPTION
Compensation pin. Output of the internal error amplifier. Capacitor and resistor from COMP pin to ground. Voltage feedback pin. Internal reference is 1.24V NOMINAL. Connect a resistor divider from VOUT. VOUT=1.24V (1+R1/R2). Shutdown control pin. Pull SHDN low to turn off the device. Analog and power ground. Power switch pin. Switch connected to the drain of the internal power MOSFET. Analog power input pin. Frequency select pin. When FSEL is connected to GND, switching frequency is set to 620kHz. When connected to VIN, switching frequency is set to 1.25MHz Soft-start control pin. Connect a capacitor to control the converter start-up
SHDN GND SW VIN FSEL SS
3 4 5 6 7 8
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Ordering Information
Order Number Package Type Marking Operating Temperature range
EUP2624MIR1
MSOP-8
xxxx P2624
-40 C to 85C
EUP2624
1/4
1/4
1/4
1/4
Lead Free Code 1: Lead Free 0: Lead Packing R: Tape & Reel Operating temperature range I: Industry Standard Package Type M: MSOP
Block Diagram
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Absolute Maximum Ratings
VIN --------------------------------------------------------------------------------------6V SW Voltages ---------------------------------------------------------------------------- 30V FB Voltage ----------------------------------------------------------------------------2V SHDN Voltage ------------------------------------------------------------------------6V Junction Temperature ------------------------------------------------------------------ 150C Lead Temp (Soldering, 10sec) --- --------------------------------------------------300C ESD Ratings Human Body Model ---------------------------------------------------------------- 2kV Operating Conditions Operating Temperature --------------------------------------------------------- -40C to 85C Supply Voltage -------------------------------------------------------------------- 2.5V to 5.5V SW Voltage Max ---------------------------------------------------------------------28V
Electrical Characteristics
VIN=VSHDN=3V. TA=-40J Symbol VIN UVLO .Typical values are at TA=25J .Unless otherwise noted. EUP2624 Parameter Conditions Min Typ Max. VOUT<18V 2.5 5.5 Input Voltage Range 18V< VOUT<24V 4.0 5.5 to 85J SW Remains off below this level. VIN Rising,20mV hysteresis FB=2V (Not Switching) IQ VFB IB %VFB/ VIN %VFB/ ILOAD gm AV Fs DMAX ICL RDSON IL ISS VIL VIH IFSLCT Quiescent Current FB Regulation Voltage FB Input Bias Current FB Line Regulation FB Load Regulation Error Amp Transconductance Error Amp Voltage Gain Switching Frequency Maximum Duty Cycle Switch Current Limit Switch MOSFET On Resistance Switch Leakage Current Charge Current SHDN, FREQ Input Low Voltage SHDN, FREQ Input High Voltage FSLCT Pull Down Current
July .2006
Unit V V mA mA uA V nA %/V mV/A
VIN Undercoltage Lockout
1.92
2.15 0.5 1.5 0.1 1.24 100 0.08 6.7
2.35 0.8 2 10 1.27 250 0.15
FB=0V] Switching^ VSHDN=0V 1.20 VFB=1.24V 2.5V VIN 5.5V VOUT=8V,Iload=30mA to200 mA I=4uA FSLCT=Ground FSLCT=VIN 55% Duty Cycle ISW=500mA VSW=20V VSS=0V 3 2 2.4 20 500 900 1.5
45 500 620 1250 94 2.1 0.17 0.2 5
95 740 1500 2.8 0.35 20 8 0.5
umho V/V kHz kHz H A uA uA V V uA
5.5
8.2
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Typical Operating Characteristics
620kHz Efficiency vs. Load Current
95 90 85 80
620kHz Switching Frequency vs. Temperature
630
VOUT=8V
VIN=5.5V
SWITCHING FREQUENCY (kHA)
620 610 600 590 580 570 560 550 -40 -30 -20 -10
EFFICIENCY (%)
75 70 65 60 55 50 45 40 35 30 1 10 100
VIN=3V VIN=2.5V
VIN=5.5V
VIN=2.5V
1000
0
10
20
30
40
0
50
60
70
80
90
LOAD CURRENT (mA)
TEMPERATURE( C)
FSLCT Pin Current vs. FSLCT Pin Voltage
6.6
Switching Current Limit vs. Temperature
3.2
FSLCT PIN CURRENT(uA)
6.4 6.2
VOUT=8V
3.0
CURRENT LIMIT (A)
6.0
T=-40 C
5.8
0
2.8
VIN=5.5V
T=25 C
5.6 5.4 5.2
0
2.6
2.4
T=85 C
0
2.2
VIN=3V VIN=2.5V
0 10 20 30 40
0
2.0
5.0 2.5
3.0
3.5
4.0
4.5
5.0
5.5
-40 -30 -20 -10
50
60
70
80
90
FSLCT VOLTAGE(V)
TEMPERATURE( C)
2.50
620kHz Switching IQ vs. Temperature
4.00 3.75
1.25MHz Switching IQ vs. Temperature
2.25
SWITCHING IQ (mA)
VIN=5.5V
3.50
VIN=5.5V
SWITCHING IQ (mA)
VIN=2.5V
2.00
3.25 3.00 2.75 2.50 2.25 2.00 1.75
1.75
1.50
1.25
VIN=2.5V
1.00 -40
-30
-20
-10
0
10
20
30
40
0
50
60
70
80
90
1.50 -40
-30
-20
-10
0
10
20
30
40
0
50
60
70
80
90
TEMPERATURE( C)
TEMPERATURE( C)
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620kHz Non-switching IQ vs. Input Voltage
0.60
0.65
1.25MHz Non-switching IQ vs. Input Voltage
T= 25 C
0
NON-SWITCHING IQ (mA)
NON-SWITCHING IQ (mA)
0.55
0.60
0.50
T= 85 C
0
T= 25 C
0
0.55
T= 85 C
0
0.45
0.50
0.40
0.45
0.35
T= - 40 C
0
0.40
T= - 40 C
0
0.30 2.5
3.0
3.5
4.0
4.5
5.0
5.5
0.35 2.5
3.0
3.5
4.0
4.5
5.0
5.5
INPUT VOLTAGE (V)
INPUT VOLTAGE (V)
620kHz Switching IQ vs. Input Voltage
2.3 2.2 2.1
4.0
1.25MHz Switching IQ vs. Input Voltage
3.5
0
SWITCHING IQ (mA)
1.9 1.8 1.7 1.6 1.5 1.4 1.3 1.2 1.1 1.0 2.5 3.0 3.5
T= 25 C
SWITCHING IQ (mA)
2.0
0
T= - 40 C
3.0
T= 25 C T= - 40 C
0
0
2.5
T= 85 C
0
T= 85 C
2.0
0
4.0
4.5
5.0
5.5
1.5 2.5
3.0
3.5
4.0
4.5
5.0
5.5
INPUT VOLTAGE (V)
INPUT VOLTAGE (V)
SS Pin Current vs. Temperature
6.8 6.6
NMOS RDSON vs. Input Voltage
0.24 0.22
SS PIN CURRENT(uA)
6.4
0.20
6.2 6.0 5.8 5.6 5.4 5.2 5.0 -40
VIN=5.5V
NMOS RDSON (O)
T = 85 C
0
0.18 0.16 0.14 0.12 0.10 2.5
T = 25 C
0
VIN=2.5V
T = - 40 C
3.0 3.5 4.0 4.5 5.0 5.5
0
-30
-20
-10
0
10
20
30
40
0
50
60
70
80
90
TEMPERATURE( C)
INPUT VOLTAGE (V)
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Application Information
Boost Converter Operations In steady state operating and continuous conduction mode where the inductor current is continuous, the boost converter operates in two cycles. During the first cycle, the internal power FET turns on and the Schottky diode is reverse biased and cuts off the current flow to the output. The output current is supplied from the output capacitor. The voltage across the inductor is VIN and the inductor current ramps up in a rate of VIN/L, L is the inductance. The inductance is magnetized and energy is stored in the inductor. The change in inductor current is:
V - VOUT I L = T2 x IN L
Inductor Selection The inductor selection determines the output ripple voltage, transient response, output current capability, and efficiency. Its selection depends on the input voltage, output voltage, switching frequency, and maximum output current. For most applications, a 4.7H inductor is recommended for 1.25MHz application and a 10H inductor is recommended for 620kHz application. The inductor maximum DC current specification must be greater than the peak inductor current required by the regulator. The peak inductor current can be calculated:
xV V x (V -V ) OUT OUT IN OUT IN I = + 1/2 x V LxV x FREQ L(PEAK) IN OUT I
T2 =
1- D F SW
For stable operation, the same amount of energy stored in the inductor must be taken out. The change in inductor current during the two cycles must be the same. I1+I2=0
V D 1 - D VIN - VOUT x IN + x =0 L F L F SW SW
Output Capacitor Low ESR capacitors should be used to minimized the output voltage ripple. Multilayer ceramic capacitors (X5R and X7R) are preferred for the output capacitors because of their lower ESR and small packages. Tantalum capacitors with higher ESR can also be used. The output ripple can be calculated as:
I xD OUT V = +I x ESR O OUT F xC SW O
V 1 OUT = 1- D V IN
Choose an output capacitor to satisfy the output ripple and load transient requirement. A 10F to 22F ceramic capacitor is suitable for most application. For noise sensitive application, a 0.1F placed in parallel with the larger output capacitor is recommended to reduce the switching noise coupled from the SW switching node. Schottky Diode In selecting the Schottky diode, the reverse break down voltage, forward current and forward voltage drop must be considered for optimum converter performance. The diode must be rated to handle 2A, the current limit of the EUP2624. The breakdown voltage must exceed the maximum output voltage. Low forward voltage drop, low leakage current, and fast reverse recovery will help the converter to achieve the maximum efficiency.
Output Voltage An external feedback resistor divider is required to divide the output voltage down to the nominal 1.24V reference voltage. The current drawn by the resistor network should be limited to maintain the overall converter efficiency. The maximum value of the resistor network is limited by the feedback input bias current and the potential for noise being coupled into the feedback pin. Selecting R2 in the range of 10k to 50 k. The boost converter output voltage s determined by the relationship:
R V =V x 1 + 1 OUT FB R 2

The nominal VFB voltage is 1.24V
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Input Capacitor The value of the input capacitor depends the input and output voltages, the maximum output current, the inductor value and the noise allowed to put back on the input line. For most applications, a minimum 10F is required. For applications that run close to the maximum output current limit, input capacitor in the range of 22F to 47F is recommended. The EUP2624 is powered from the VIN. High frequency 0.1F by-pass cap is recommended to be close to the VIN pin to reduce supply line noise and ensure stable operation. Loop Compensation The EUP2624 incorporates an transconductance amplifier in its feedback path to allow the user some adjustment on the transient response and better regulation. The EUP2624 uses current mode control architecture which has a fast current sense loop and a slow voltage feedback loop. The fast current feedback loop does not require any compensation. The slow voltage loop must be compensated for stable operation. The compensation network is a series RC network from COMP pin to ground. The resistor sets the high frequency integrator gain for fast transient response and the capacitor sets the integrator zero to ensure loop stability. For most applications,the compensation resistor in the range of 2K to 30K and the compensation capacitor in the range of 1nF to 10nF. Soft-Start The soft-start is provided by an internal 5A current source charges the external CSS, the peak MOSFET current is limited by the voltage on the capacitor. This in turn controls the rising rate of the output voltage. The regulator goes through the start-up sequence as well after the SHDN pin is pulled to HI. Frequency Selection The EUP2624 switching frequency can be user selected to operate at either at constant 620kHz or 1.25MHz. Connecting FSEL pin to ground sets the PWM switching frequency to 620kHz. When connect FSEL high or VDD, switching frequency is set to 1.25MHz. Shut-Down Control The EUP2624 shuts down to reduce the supply current to 0.1g A when SHDN is low. In this mode, the internal reference, error amplifier, comparators, and biasing circuitry turn off while the N-channel MOSFET is turned off. The boost converter's output is connected to IN via the external inductor and catch diode. Maximum Output Current The output current capability of the EUP2624 is a function of current limit, input voltage, operating frequency, and inductor value. The output current capability is governed by the following equation:
I L = I L - AVG + 1 / 2 x I L
(
)
Where: IL=MOSET current limit I L - AVG =average inductor current
I L =inductor ripple current
I L =
VIN x VO + VDIODE - V - VIN IN L x VO + V DIODE
x F S
VDIODE = Schottky diode forward voltage, typically, 0.6V FS = switching frequency, 620KHz or 1.25MHz
I I L - AVG = OUT 1-D
D = MOSFET turn-on ratio:
D =1- VIN VOUT + V DIODE
Layout Considerations Good PC board layout and routing are required in high-frequency switching power supplies to achieve good regulation, high efficiency, and stability. It is strongly recommended that the evaluation kit PC board layouts be followed as closely as possible. Place power components as close together as possible, keeping their traces short, direct, and wide. Avoid interconnecting the ground pins of the power components using vias through an internal ground plane. Instead, keep the power components close together and route them in a "star" ground configuration using component-side coper, then connect the star ground to internal ground using multiple vias.
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Packaging Information
MSOP-8
NOTE 1. Package body sizes exclude mold flash and gate burrs 2. Dimension L is measured in gage plane 3. Tolerance 0.10mm unless otherwise specified 4. Controlling dimension is millimeter. Converted inch dimensions are not necessarily exact. SYMBOLS A A1 A2 b C D E E1 e L y c DIMENSIONS IN MILLIMETERS MIN. NOM. MAX. 0.81 0.95 1.10 0.05 0.09 0.15 0.76 0.86 0.97 0.28 0.30 0.38 0.13 0.15 0.23 2.90 3.00 3.10 4.70 4.90 5.10 2.90 3.00 3.10 -----0.65 ----0.40 0.53 0.66 ----------0.10 0 -----6 DIMENSIONS IN INCHES MIN. NOM. MAX. 0.032 0.0375 0.043 0.002 0.004 0.006 0.030 0.034 0.038 0.011 0.012 0.015 0.005 0.006 0.009 0.114 0.118 0.122 0.185 0.193 0.201 0.114 0.118 0.122 -----0.026 -----0.016 0.021 0.026 ----------0.004 0 -----6
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