Eutech EUP3410 2a,16v,380khz step-down converter Datasheet

EUP3410/3411
2A,16V,380KHz Step-Down Converter
DESCRIPTION
FEATURES
The EUP3410/3411 is a current mode, step-down
switching regulator capable of driving 2A continuous
load with excellent line and load regulation. The
EUP3410/3411 can operate with an input voltage range
from 4.5V to 16V and the output can be externally set
from 1.2V to 12V with a resistor divider.
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Fault condition protection includes cycle-by-cycle
current limiting and thermal shutdown. In shutdown
mode the regulator draws 25µA of supply current.
The EUP3410/3411 requires a minimum number of
external components.
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30V Input Surge Protection
Up to 2A Output Current
0.17Ω Internal DMOS Output Switch
4.5V to 16V Input Operating Range
Output Adjustable from 1.2V to 12V
Up to 95% Efficiency
25µA Shutdown Current
Fixed 380KHz Frequency
Thermal Shutdown and Overcurrent Protection
Input Supply Overvoltage and Undervoltage
Lockout
Available in SOP-8 & MSOP-10 Packages
RoHS Compliant and 100% Lead(Pb)-Free
APPLICATIONS
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PC Monitors
Distributed Power Systems
Networking Systems
Portable Electronics
Typical Application Circuit
Figure 1. Typical Application Circuit with Ceramic Capacitors
DS3410/3411
Ver1.2
Nov. 2008
1
EUP3410/3411
Typical Application Circuit (continued)
Figure 2. Typical Application Circuit with Electrolytic Capacitors
Block Diagram
Figure 3. Functional Block Diagram
DS3410/3411
Ver1.2
Nov. 2008
2
EUP3410/3411
Pin Configurations
Package
Type
Pin
Package
Type
Configurations
SOP-8
Pin
Configurations
MSOP-10
Pin Description
Pin Name
EUP3410
EUP3411
BS
1
2
IN
2
4
SW
3
5
High-Side Gate Driver Boostrap Supply. BS provides power to the gate
driver of high-side n-channel MOSFET switch. Connect a 10nF or greater
capacitor from SW to BS.
Input Supply Pin. IN supplies the power to the IC and the high side
power switch. Connect IN to a 4.5V to 16V power source. Bypass IN to
GND with a suitably large value capacitor to minimize input ripple to
the IC. See Input Capacitor Section of the applications notes.
Power Switcher Output. Connect the output LC filter from SW to the output.
GND
4
6
Ground.
FB
5
7
COMP
6
8
EN
7
9
NC
8
1,3
SS
-
10
DS3410/3411
Ver1.2
Nov. 2008
DESCRIPTION
Output Feedback Input. FB senses the output voltage to regulate that
voltage. Connect FB to an external resistor divider to set the output voltage.
The feedback threshold is 1.2V. See Setting the Output Voltage.
Loop compensation pin. Connect a series RC network from COMP to GND
to compensate the regulation control loop. See Compensation.
Enable Input. EN is a logic input that controls the regulator on or off.
Drive EN logic high to turn on the regulator, and set EN logic low to
turn it off. For automatic startup, leave EN unconnected and EN is pulled
high by an internal current source to enable the device.
No Connect
Soft-Start pin. Connect SS to an external capacitor to program the soft-start
time. If the pin is not used, leave it open.
3
EUP3410/3411
Ordering Information
Order Number
Package Type
EUP3410DIR1
SOP-8
EUP3411MIR1
MSOP-10
EUP3410/3411
Marking
xxxxx
P3410
xxxxx
3411A
□ □ □ □
Lead Free Code
1: Lead Free 0: Lead
Packing
R: Tape & Reel
Operating temperature range
I: Industry Standard
Package Type
D: SOP
M: MSOP
DS3410/3411
Ver1.2
Nov. 2008
4
Operating Temperature Range
-40°C to +85°C
-40 °C to +85°C
EUP3410/3411
Absolute Maximum Ratings (1)
„
„
„
„
„
„
„
„
„
Input Voltage (VIN)
------------------------------------------------------------ -0.3V to 30V
Switch Voltage (VSW) ------------------------------------------------------ -1V to VIN +0.3V
Boot Strap Voltage (VBS) ------------------------------------------------ VSW-0.3V to VSW +6V
All Other Pins --------------------------------------------------------------------- -0.3V to 6V
Junction Temperature ------------------------------------------------------------------- 150°C
Storage Temperature
------------------------------------------------------ -65°C to +150°C
Lead Temp (Soldering, 10sec) ------------------------------------------------------260°C
Thermal Resistance θJA (SOP-8) ----------------------------------------------------- 90°C/W
Thermal Resistance θJA (MSOP-10) --------------------------------------------- 61.11°C/W
Recommend Operating Conditions (2)
„
„
Supply Voltage (VIN) ------------------------------------------------------------- 4.5V to 16V
Operating Temperature Range ----------------------------------------------- -40°C to +85°C
Note (1): Stress beyond those listed under “Absolute Maximum Ratings” may damage the device.
Note (2): The device is not guaranteed to function outside the recommended operating conditions
Electrical Characteristics
Unless otherwise specified, VEN=5V, VIN=12V ,TA=+25°C.
Parameter
Feedback Voltage
Upper Switch On Resistance
Lower Switch On Resistance
Upper Switch Leakage
Switch Peak Current Limit
Oscillator Frequency
Short Circuit Frequency
Maximum Duty Cycle
Minimum Duty Cycle
Enable Threshold
Input Undervoltage Lockout
Threshold Rising
Input Undervoltage Lockout
Threshold Hysteresis
Input Overvoltage Lockout Threshold
Shutdown Supply Current
Operating Supply Current
Soft-Start Current (EUP3411)
Thermal Shutdown
DS3410/3411
Ver1.2
Nov. 2008
Conditions
4.5V ≤ VIN ≤ 16V
EUP3410/3411
Min
Typ
Max
1.162
1.200
0.17
6.8
2.4
320
0.7
3
380
45
90
0
0.95
2
2.5
VEN=0V, VSW=0V
1.236
1.4
V
Ω
Ω
µA
A
KHz
KHz
%
%
V
3
V
5
VFB=0V
VFB=1V
VFB=1.5V
440
110
22
25
0.45
5.2
160
VEN=0V
VFB=1.4V
VSS=0V
5
Unit
mV
36
0.7
V
µA
mA
uA
°C
EUP3410/3411
Typical Operating Characteristics
See Figure 2.C1=390uF, C2=0.22uF, C6=0.22uF, C7=560uF, L=15uH, TA= +25℃.
DS3410/3411
Ver1.2
Nov. 2008
6
EUP3410/3411
Typical Operating Characteristics
See Figure 2.C1=390uF, C2=0.22uF, C6=0.22uF, C7=560uF, L=15uH, TA= +25℃.
DS3410/3411
Ver1.2
Nov. 2008
(EUP3410)
(EUP3410)
(EUP3411)
(EUP3411)
7
EUP3410/3411
Typical Operating Characteristics
See Figure 2.C1=390uF, C2=0.22uF, C6=0.22uF, C7=560uF, L=15uH, TA= +25℃.
DS3410/3411
Ver1.2
Nov. 2008
8
EUP3410/3411
Functional Description
The EUP3410/3411 is a current-mode step-down
switching regulator. The device regulates an output
voltage as low as 1.2V from a 4.5V to 16V input power
supply. The device can provide up to 2Amp continuous
current to the output. The EUP3410/3411 uses
current-mode architecture to control the regulator loop.
The output voltage is measured at FB through a resistive
voltage divider and amplified through the internal error
amplifier. The output current of the transconductance
error amplifier is presented at COMP pin where a RC
network compensates the regulator loop. Slope
compensation is internally added to eliminate
subharmonic oscillation at high duty cycle. The slope
compensation adds voltage ramp to the inductor current
signal which reduces maximum inductor peak current at
high duty cycles.
The device uses an internal Hside n-channel switch to
step down the input voltage to the regulated output
voltage. Since the Hside n-channel switch requires gate
voltage greater than the input voltage, a boostrap BS
capacitor is connected between SW and BS to drive the
n-channel gate. The BS capacitor is internally charged
while the switch is off. An internal 6.8Ω switch from SW
to GND is added to insure that SW is pulled to GND
when the switch is off to fully charge the BS capacitor.
Application Information
Setting the Output Voltage
The output voltage is set through a resistive voltage
divider (see Figure1 or 2). The voltage divider divides
the output voltage down by the ratio:
VFB = VOUT ∗ R 3 / (R 2 + R 3) = 1.2 V
Thus the output voltage is :
VOUT = 1.2 V ∗ (R 2 + R 3) / R 3
Choose R3 value in the range 10k to 100k, R2 is
determined by :
R 2 = (VOUT / 1.2 − 1) ∗ R 3
Inductor
The inductor is required to supply constant current to the
output load while being driven by the switched input
voltage. A larger value inductor results in less ripple
current and lower output ripple voltage. However, the
larger value inductor has a larger physical size, higher
series resistance, and lower saturation current. Choose
an inductor that does not saturate under the worst-case
load conditions. A good rule for determining the
inductance is to allow the peak-to- peak ripple current in
the inductor to be approximately 30% of the maximum
load current. Also, make sure that the peak inductor
Ver1.2
Nov. 2008
L = (VOUT ) ∗ (VIN − VOUT ) / (VIN ∗ f ∗ ∆I )
Where VOUT is the output voltage, VIN is the input
voltage, f is the switching frequency, and ∆I is the
peak-to-peak inductor ripple current.
Input Capacitor
The input current to the step-down converter is
discontinuous, and therefore an input capacitor C1 is
required to supply the AC current to the step-down
converter while maintaining the DC input voltage. A low
ESR capacitor is required to keep the noise minimum at
the IC. Ceramic capacitors are preferred, but tantalum or
low-ESR electrolytic capacitors may also suffice. The
input capacitor value should be greater than 10µF, and
the RMS current rating should be greater than
approximately 1/2 of the DC load current. In Figure 2,
for insuring stable operation C2 should be placed as
close to the IC as possible. Alternately a smaller high
quality ceramic 0.1µF capacitor may be placed closer to
the IC and a larger capacitor placed further away. If
using this technique, it is recommended that the larger
capacitor type are either tantalum or electrolytic. In
Figure 1, all ceramic capacitors should be placed close
to the EUP3410/3411.
Output Capacitor
The output capacitor is required to maintain the DC
output voltage. Low ESR capacitors are preferred to
keep the output voltage ripple low. The characteristics of
the output capacitor also affect the stability of the
regulator control loop. Ceramic, tantalum, or low ESR
electrolytic capacitors are recommended. In the case
of ceramic capacitors, the impedance at the switching
frequency is dominated by the capacitance. The output
voltage ripple is estimated to be:
VRIPPLE ~ = 1.4 ∗ VIN ∗ (f LC / f )∧ 2
For example, for a 3.3V output voltage, R3 is 10KΩ, and
R2 is 17.5KΩ.
DS3410/3411
current (the load current plus half the peak-to-peak
inductor ripple current) is below the 2.4A minimum peak
current limit.
The inductance value can be calculated by the equation:
9
Where VRIPPLE is the output ripple voltage, VIN is the
input voltage, fLC is the resonant frequency of the LC
filter, f is the switching frequency. In the case of
tanatalum or low ESR electrolytic capacitors, the ESR
dominates the impedance at the switching frequency, and
so the output ripple is calculated as:
VRIPPLE ~ = ∆I ∗ R ESR
Where VRIPPLE is the output voltage ripple, ∆I is the
inductor ripple current, and RESR is the equivalent series
resistance of the output capacitors.
EUP3410/3411
Output Rectifier Diode
The output rectifier diode supplies the current to the
inductor when the high-side switch is off. A schottky
diode is recommended to reduce losses due to the diode
forward voltage and recovery times.
Loop Compensation
The system stability is controlled through the COMP pin.
COMP is the output of the internal transconductance
error amplifier. A series capacitor-resistor combination
sets a pole-zero combination to control the feedback
loop.
The DC loop gain is:
A VDC = (VFB / VOUT ) ∗ A VEA ∗ G CS ∗ R LOAD
crossover frequency, fC, of 40KHz. Lower crossover
frequency results in slower loop response and poor load
transient performance. Higher crossover frequency can
result in loop instability.
Table 1. Compensation Values for Typical Output
Voltage /Capacitor Combinations
VOUT
C7
R1
C5
C4
2.5V
3.3V
5V
12V
22µF Ceramic
22µF Ceramic
22µF Ceramic
22µF Ceramic
560µF/6.3V
(30mΩ ESR)
560µF/6.3V
(30mΩ ESR)
470µF/10V
(30mΩ ESR)
220µF/25V
(30mΩ ESR)
10KΩ
10KΩ
10KΩ
10KΩ
3.9nF
3.9nF
3.9nF
3.9nF
None
None
None
None
10KΩ
30nF
None
10KΩ
39nF
None
10KΩ
47nF
None
10KΩ
56nF
None
2.5V
3.3V
Where:
5V
VFB is the feedback threshold voltage, 1.2V
12V
VOUT is the desired output regulation voltage
AVEA is the transconductance error amplifier voltage
gain, 400 V/V
GCS is the current sense gain, (roughly the output current
divided by the voltage at COMP), 2A/V
RLOAD is the load resistance (VOUT / IOUT where IOUT is
the output load current)
The system has 2 poles. One is due to the compensation
capacitor (C5), and the other is due to the output
capacitor (C7). These are:
f P1 = G EA / (2 π ∗ A VEA ∗ C5 )
Where P1 is the first pole, and GEA is the error amplifier
transconductance (660µA/V).
and
f P 2 = 1 / (2 π ∗ R LOAD ∗ C 7 )
The system has one zero of importance, due to the
compensation capacitor (C5) and the compensation
resistor (R1). The zero is:
f Z1 = 1 / (2 π ∗ R1 ∗ C5 )
If a large value capacitor (C7) with relatively high
equivalent-series-resistance (ESR) is used, the zero due
to the capacitance and ESR of the output capacitor can
be compensated by a third pole set by R1 and C4. The
pole is:
f P3 = 1/ (2π ∗ R1 ∗ C4 )
The system crossover frequency (the frequency where
the loop gain drops to 1, or 0dB) is important. A good rule
of thumb is to set the crossover frequency to
approximately 1/10 of the switching frequency. In this
case, the switching frequency is 380KHz, therefore use a
DS3410/3411 Ver1.2 Nov. 2008
10
The values of the compensation components listed in
Table 1 yield a stable control loop for the given output
voltage.
EUP3410/3411
Packaging Information
SOP-8
SYMBOLS
MILLIMETERS
MIN.
MAX.
MIN.
A
1.35
1.75
0.053
0.069
A1
0.10
0.25
0.004
0.010
D
E
4.90
5.80
E1
Ver1.2
MAX.
0.193
6.20
0.228
3.90
0.244
0.153
L
0.40
1.27
0.016
0.050
b
0.31
0.51
0.012
0.020
e
DS3410/3411
INCHES
Nov. 2008
1.27
0.050
11
EUP3410/3411
MSOP-10
SYMBOLS
A
A1
D
E1
E
L
b
e
D1
E2
DS3410/3411
Ver1.2
Nov. 2008
MILLIMETERS
MIN.
MAX.
1.10
0.00
0.15
3.00
3.00
4.70
5.10
0.40
0.80
0.17
0.33
0.50
1.80
1.66
12
INCHES
MIN.
0.000
MAX.
0.043
0.006
0.118
0.118
0.185
0.016
0.006
0.201
0.031
0.013
0.020
0.071
0.065
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