EC3292NNMHR [E-CMOS]
2A, 18V, Synchronous Step-down DC/DC Converter;
| 型号： | EC3292NNMHR |
| 厂家： | 
E-CMOS Corporation |
| 描述： | 2A, 18V, Synchronous Step-down DC/DC Converter |
| 文件： | 总10页 (文件大小：764K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
EC3292
2A, 18V, Synchronous Step-down DC/DC Converter
General Description
Features
The EC3292 is a high-frequency, synchronous, rectified,
step-down, switch-mode converter with internal power
MOSFETs. It offers a very compact solution to achieve
a 2A continuous output current over a wide input supply
range, with excellent load and line regulation.
The EC3292 has synchronous-mode operation for higher
efficiency over the output current-load range.
Current-mode operation provides fast transient response
and eases loop stabilization.
Protection features include over-current protection and
thermal shutdown.
The EC3292 requires a minimal number of readily
available, standard external components and is available
in a space-saving SOP-8L(Exposed Pad) package.
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4.75V to 18V input voltage
Output adjustable from 0.923V to 15V
Output current up to 2A
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Integrated 135mΩ/100mΩ power MOSFET switches
Shutdown current 3μA typical
Efficiency up to 95%
Programmable switching frequency up to 1.5MHz
Internal soft start
Over current protection and Hiccup
Over temperature protection
RoHS Compliant and 100% Lead (Pb) Free
Applications
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Distributed power systems
Networking systems
FPGA, DSP, ASIC power supplies
Notebook computers
Green electronics or appliance
Pin Assignments
Pin Description
Pin
Symbol
Description
1
2
3
4
5
6
7
8
BOOT
IN
High-side Gate drive boost input.
Power Input
SW
Power Switching Output.
Ground.
GND
FB
Feedback input.
COMP
EN
Compensation node
Enable Input.
FREQ
Switching Frequency Program Input.
E-CMOS Corp. (www.ecmos.com.tw)
Page 1 of 10
3L03N-Rev.P001
EC3292
2A, 18V, Synchronous Step-down DC/DC Converter
Ordering Information
Part Number
Package
Marking
Marking Information
1. LLLLL：Lot No
2. YYWW：Date Code
EC3292
LLLLL
YYWWT
SOP-8L
(Exposed Pad)
EC3292NNMHR
3. T：Internal Tracking Code
Functional Block Diagram
E-CMOS Corp. (www.ecmos.com.tw)
Page 2 of 10
3L03N-Rev.P001
EC3292
2A, 18V, Synchronous Step-down DC/DC Converter
Typical Application Circuit
Note: R5 and C7 are optional.
Details please see the DVT report.
Absolute Maximum Ratings
Supply Voltage VIN ……………………………….... –0.3V to +20V
Switch Node VSW ………………………………. –0.3V to VIN+0.3V
Boost VBOOT …………………………………… VSW–0.3V to VSW+6V
All Other Pins …………………………………………… –0.3V to +6V
Junction Temperature ………………………………………. +150°C
Lead Temperature …………………………………………….. +260°C
Storage Temperature Range …………......
–65°C to +150°C
CAUTION: Stresses above those listed in “Absolute Maximum Ratings” may cause permanent damage to the device.
This is a stress only rating and operation of the device at these or any other conditions above those indicated in the operational
sections of this specification is not implied.
Recommended Operating Conditions
Supply Voltage VIN …...…………...…….……… 4.75V to 18V
Output Voltage VOUT ……...…………...……. 0.923V to VIN–3V
Operating Temperature Range ……...…… –40°C to +125°C
Package Thermal Characteristics
Thermal Resistance, θJA ……………………………………. 50°C/W
Thermal Resistance, θJC ……………………………………. 10°C/W
E-CMOS Corp. (www.ecmos.com.tw)
Page 3 of 10
3L03N-Rev.P001
EC3292
2A, 18V, Synchronous Step-down DC/DC Converter
Electrical Characteristics
(TA = +25°C, VIN = +12V, unless otherwise noted.)
PARAMETER
TEST CONDITIONS
MIN
TYP
MAX
UNIT
Symbol
4.75
18
15
6
V
V
Supply Voltage
Output Voltage
VIN
0.923
VOUT
Shutdown Supply Current
Supply Current
3
µA
mA
V
VEN = 0V
0.09
0.923
1.01
1000
120
VEN = 2.0V, VFB = 1.0V
4.75V ≤ VIN ≤ 18V
0.9
0.946
Feedback Voltage
VFB
Feedback Over-voltage Threshold
V
V/V
µA/V
mΩ
mΩ
Error Amplifier Voltage Gain *
AEA
GEA
Error Amplifier Transconductance
High-Side Switch-On Resistance *
Low-side Switch-On Resistance *
ΔIC = ±10μA
135
RDS(ON)1
RDS(ON)2
100
VEN = 0V, VSW = 0V,
TA = +125°C
High-Side Switch Leakage Current
10
µA
Upper Switch Current Limit
Lower Switch Current Limit
Minimum Duty Cycle
From Drain to Source
3
3.6
0
A
A
2.8
A/V
KHz
KHz
%
COMP to Current Sense Transconducta
Oscillation Frequency
GCS
400
100
500
125
90
600
150
FOSC1
FOSC2
DMAX
Rfreq = 175K
Rfreq = 175K, VFB = 0
VFB = 0.5V
Short Circuit Oscillation Frequency
Maximum Duty Cycle
Minimum On Time *
120
1.22
1.32
3.75
ns
V
EN Falling Threshold Voltage
EN Rising Threshold Voltage
Input Under Voltage Lockout Threshold
VEN Falling
VEN Rising
VIN Rising
V
V
Input Under Voltage Lockout Threshold
Hysteresis
200
mV
Soft-Start Period
Fsw = 500KHz
16
ms
°C
Thermal Shutdown *
150
* Guaranteed by design, not tested.
E-CMOS Corp. (www.ecmos.com.tw)
Page 4 of 10
3L03N-Rev.P001
EC3292
2A, 18V, Synchronous Step-down DC/DC Converter
Typical Characteristics
VIN = 12V, VO = 3.3V, L1 = 4.7μH, C1 = 10μF, C2 = 10μF x 2, TA = +25°C, unless otherwise noted.
Start UP & Inrush Current 12V→3.3V (Load 1A)
Shut Down (Iout 1A→Shut down)
Output Ripple (12V => 3.3V, Load=2A)
Output Ripple (12V => 3.3V, Load=1A)
Output Ripple (12V => 3.3V, Load=0A)
Dynamic Load (Iload=0.2A_2AVout=3.3V)
Short Circuit Protection
Efficiency
E-CMOS Corp. (www.ecmos.com.tw)
Page 5 of 10
3L03N-Rev.P001
EC3292
2A, 18V, Synchronous Step-down DC/DC Converter
Application Information
Overview
FB: Feedback Input. FB senses the output voltage to
regulate that voltage. Drive FB with a resistive voltage
divider from the output voltage. The feedback threshold
is 0.923V.
The EC3292 is a synchronous rectified, current-mode,
step-down regulator. It regulates input voltages from
4.75V to 18V down to an output voltage as low as
0.923V, and supplies up to 2A of load current.
The EC3292 uses current-mode control to regulate
the output voltage. The output voltage is measured at
FB through a resistive voltage divider and amplified
through the internal transconductance error amplifier.
The voltage at the COMP pin is compared to the switch
current measured internally to control the output
voltage.
The converter uses internal N-Channel MOSFET switches
to step-down the input voltage to the regulated output
voltage. Since the high side MOSFET requires a gate
voltage greater than the input voltage, a boost capacitor
connected between SW and BOOT is needed to drive
the high side gate. The boost capacitor is charged from
the internal 5V rail when SW is low.
COMP: Compensation Node.COMP is used to compensate.
the regulation control loop. Connect a series RC
network from COMP to GND to compensate the
regulation control loop. In some cases, an additional
capacitor from COMP to GND is required.
EN: Enable Input. EN is a digital input that turns the
regulator on or off. Drive EN high to turn on the
regulator, drive it low to turn it off. Pull up with 100kΩ
resistor for automatic startup.
FREQ: Switching Frequency Program Input. Connect a
resistor from this pin to ground to set the switching
frequency.
Setting the Output Voltage
When the EC3292 FB pin exceeds 10% of the
nominal regulation voltage of 0.923V, the over voltage
comparator is tripped and the COMP pin is discharged
to GND, forcing the high-side switch off.
The output voltage is set using a resistive voltage divider
from the output voltage to FB pin. The voltage divider
divides the output voltage down to the feedback voltage
by the ratio:
Pins Description
VFB = VOUT × R2 / (R1 + R2)
Where VFB is the feedback voltage and VOUT is the output
voltage.
Thus the output voltage is:
BOOT: High-Side Gate Drive Boost Input. BOOT supplies
the drive for the high-side N-Channel MOSFET switch.
Connect a 0.1μF or greater capacitor from SW to BOOT
to power the high side switch.
VOUT = 0.923 × (R1 + R2) / R2
R2 can be as high as 100kΩ, but a typical value is 10kΩ.
Using the typical value for R2, R1 is determined by:
R1 = 10.83 × (VOUT − 0.923V) (KΩ)
IN: Power Input. IN supplies the power to the IC, as well
as the step-down converter switches. Drive IN with a
4.75V to 18V power source. Bypass IN to GND with a
suitably large capacitor to eliminate noise on the input
to the IC.
Programmable Oscillator
The EC3292 oscillating frequency is set by an
external resistor, Rfreq from the FREQ pin to ground. The
value of Rfreq can be calculated from:
SW: Power Switching Output. SW is the switching node
that supplies power to the output. Connect the output
LC filter from SW to the output load. Note that a
capacitor is required from SW to BOOT to power the
high-side switch.
Rfreq(KΩ) = 87000/FOSC1(KHz)
Inductor
GND: Ground.
The inductor is required to supply constant current to
the output load while being driven by the switched
input voltage. A larger value inductor will result in less
E-CMOS Corp. (www.ecmos.com.tw)
Page 6 of 10
3L03N-Rev.P001
EC3292
2A, 18V, Synchronous Step-down DC/DC Converter
switching current it requires an adequate ripple current
rating. The RMS current in the input capacitor can be
Application Information(Cont.)
ripple current that will result in lower output ripple
voltage. However, the larger value inductor will have a
larger physical size, higher series resistance, and/or
lower saturation current. A good rule for determining
the inductance to use is to allow the peak-to-peak ripple
current in the inductor to be approximately 30% of the
maximum switch current limit. Also, make sure that the
peak inductor current is below the maximum switch
current limit. The inductance value can be calculated by:
L = [ VOUT / (fS × ΔIL) ] × (1 − VOUT/VIN)
Where VOUT is the output voltage, VIN is the input voltage,
fS is the switching frequency, and ΔIL is the peak-to-peak
inductor ripple current.
Choose an inductor that will not saturate under the
maximum inductor peak current. The peak inductor
current can be calculated by:
estimated by:
IC1 = ILOAD × [ (VOUT/VIN) × (1 − VOUT/VIN) ] 1/2
The worst-case condition occurs at VIN = 2VOUT, where IC1
= ILOAD/2. For simplification, choose the input capacitor
whose RMS current rating greater than half of the
maximum load current.
The input capacitor can be electrolytic, tantalum or
ceramic. When using electrolytic or tantalum capacitors,
a small, high quality ceramic capacitor, i.e. 0.1μF, should
be placed as close to the IC as possible. When using
ceramic capacitors, make sure that they have enough
capacitance to provide sufficient charge to prevent
excessive voltage ripple at input. The input voltage
ripple for low ESR capacitors can be estimated by:
ILP = ILOAD + [ VOUT / (2 × fS × L) ] × (1 − VOUT/VIN)
Where ILOAD is the load current.
The choice of which style inductor to use mainly
depends on the price vs. size requirements and any EMI
requirements.
ΔVIN = [ ILOAD/(C1 × fS) ] × (VOUT/VIN) × (1 − VOUT/VIN)
Where C1 is the input capacitance value.
Output Capacitor
Optional Schottky Diode
During the transition between high-side switch and
low-side switch, the body diode of the low-side power
MOSFET conducts the inductor current. The forward
voltage of this body diode is high. An optional Schottky
diode may be paralleled between the SW pin and GND
pin to improve overall efficiency. Table 1 lists example
Schottky diodes and their Manufacturers.
The output capacitor is required to maintain the DC
output voltage. Ceramic, tantalum, or low ESR
electrolytic capacitors are recommended. Low ESR
capacitors are preferred to keep the output voltage
ripple low. The output voltage ripple can be estimated
by:
ΔVOUT = [ VOUT/(fS × L) ] × (1 − VOUT/VIN)
× [ RESR + 1 / (8 × fS × C2) ]
Part
Number
B130
Voltage and
Current Ratin
30V, 1A
Vendor
Diodes Inc.
Diodes Inc.
Where C2 is the output capacitance value and RESR is the
equivalent series resistance (ESR) value of the output
capacitor.
SK13
30V, 1A
30V, 1A
MBRS130
International Rectifier
In the case of ceramic capacitors, the impedance at the
switching frequency is dominated by the capacitance.
The output voltage ripple is mainly caused by the
capacitance. For simplification, the output voltage ripple
Table 1. Diode Selection guide
Input Capacitor
can be estimated by:
ΔVOUT = [ VOUT/(8 × fS2 × L × C2) ] × (1 − VOUT/VIN)
In the case of tantalum or electrolytic capacitors, the
ESR dominates the impedance at the switching
frequency. For simplification, the output ripple can be
approximated to:
The input current to the step-down converter is discontinuous,
therefore a capacitor is required to supply the AC current to
the step-down converter while maintaining the DC input voltage.
Use low ESR capacitors for the best performance. Ceramic capacitors
are preferred, but tantalum or low-ESR electrolytic
ΔVOUT = [ VOUT/(fS × L) ] × (1 − VOUT/VIN) × RESR
The characteristics of the output capacitor also affect
the stability of the regulation system. The EC3292
capacitors may also suffice. ChooseX5R or X7R
dielectrics when using ceramic capacitors.
Since the input capacitor (C1) absorbs the input
E-CMOS Corp. (www.ecmos.com.tw)
Page 7 of 10
3L03N-Rev.P001
EC3292
2A, 18V, Synchronous Step-down DC/DC Converter
can be optimized for a wide range of capacitance and
ESR values.
The system crossover frequency where the feedback
loop has the unity gain is important. Lower crossover
frequencies result in slower line and load transient
responses, while higher crossover frequencies could
cause system instability. A good rule of thumb is to set
Compensation Components
EC3292 employs current mode control for easy
compensation and fast transient response. The system
stability and transient response are controlled through
the COMP pin. COMP pin is the output of the internal
transconductance error amplifier. A series capacitor and
resistor combination sets a pole-zero combination to
control the characteristics of the control system.
The DC gain of the voltage feedback loop is given by:
AVDC = RLOAD × GCS × AEA × VFB/VOUT
the
crossover
frequency
below one-tenth of
the switching frequency.
To optimize the compensation components, the
following procedure can be used.
1. Choose the compensation resistor (R3) to set the
desired crossover frequency.
Determine the R3 value by the following equation:
R3 = [ (2π × C2 × fC) / (GEA × GCS) ] × (VOUT/VFB)
< [ (2π × C2 × 0.1 × fS) / (GEA × GCS) ] × (VOUT/VFB)
Where fC is the desired crossover frequency which is
typically below one tenth of the switching frequency.
2. Choose the compensation capacitor (C3) to achieve
the desired phase margin. For applications with typical
inductor values, setting the compensation zero, fZ1,
below one-forth of the crossover frequency provides
sufficient phase margin.
Where AEA is the error amplifier voltage gain; GCS is the
current sense transconductance and RLOAD is the load
resistor value.
The system has two poles of importance. One is due to
the compensation capacitor (C3) and the output resistor
of the error amplifier, and the other is due to the output
capacitor and the load resistor. These poles are located
at:
fP1 = GEA / (2π × C3 × AEA)
fP2 = 1 / (2π × C2 × RLOAD
)
Determine the C3 value by the following equation:
C3 > 4 / (2π × R3 × fC)
Where GEA is the error amplifier transconductance.
The system has one zero of importance, due to the
compensation capacitor (C3) and the compensation
resistor (R3). This zero is located at:
Where R3 is the compensation resistor.
3. Determine if the second compensation capacitor (C6)
is required. It is required if the ESR zero of the output
capacitor is located at less than half of the switching
frequency, or the following relationship is valid:
1 / (2π × C2 × RESR) < fS/2
fZ1 = 1 / (2π × C3 × R3)
The system may have another zero of importance, if the
output capacitor has a large capacitance and/or a high
ESR value. The zero, due to the ESR and capacitance of
the output capacitor, is located at:
If this is the case, then add the second compensation
capacitor (C6) to set the pole fP3 at the location of the
ESR zero. Determine the C6 value by the equation:
C6 = (C2 × RESR) / R3
fESR = 1 / (2π × C2 × RESR
)
In this case, a third pole set by the compensation
capacitor (C6) and the compensation resistor (R3) is
used to compensate the effect of the ESR zero on
the loop gain. This pole is located at:
fP3 = 1 / (2π × C6 × R3)
The goal of compensation design is to shape
the converter transfer function to get a desired loop
gain.
E-CMOS Corp. (www.ecmos.com.tw)
Page 8 of 10
3L03N-Rev.P001
EC3292
2A, 18V, Synchronous Step-down DC/DC Converter
External Bootstrap Diode
An external bootstrap diode may enhance the efficiency
of the regulator, the applicable conditions of external
BOOT diode are:
PCB Layout Guide
PCB layout is very important to achieve stable operation.
Please follow the guidelines below.
● VOUT = 5V or 3.3V; and
● Duty cycle is high: D = VOUT/VIN > 65%
In these cases, an external BOOT diode is recommended
from the output of the voltage regulator to BOOT pin, as
shown in Figure 1.
1) Keep the path of switching current short and
minimize the loop area formed by Input capacitor,
high-side MOSFET and low-side MOSFET.
2) Bypass ceramic capacitors are suggested to be put
close to the VIN Pin.
3) Ensure all feedback connections are short and direct.
Place the feedback resistors and compensation
components as close to the chip as possible.
4) Rout SW away from sensitive analog areas such as
FB.
5) Connect IN, SW, and especially GND respectively to a
large copper area to cool the chip to improve thermal
performance and long-term reliability.
BOM of EC3292
Please refer to the Typical Application Circuit.
Figure 1: Add optional external bootstrap diode to
enhance efficiency.
Item
Reference
Part
10μF
100nF
0.1μF
100K
1
2
3
4
C1
C5
C7
R4
The recommended external BOOT diode is IN4148, and
the BOOT capacitor is 0.1 ~ 1μF.
When VIN ≤ 6V, for the purpose of promote the
efficiency, it can add an externalSchottky diode
between IN and BOOT pins, as shown in Figure 2.
Table 2: BOM selection table I.
Figure 2: Add a Schottky diode to promote efficiency
when VIN ≤ 6V.
L1
R1
44.2K
25.7K
17.1K
9.5K
R2
R3
C2
C3
C8
R
freq
Vout = 5.0V
Vout = 3.3V
Vout = 2.5V
Vout = 1.8V
Vout = 1.2V
Vout = 1.0V
6.8uH
4.7uH
4.7uH
3.3uH
2.2uH
2.2uH
10K
10K
10K
10K
10K
10K
100K
100K
100K
100K
62K
10uFx2
10uFx2
10uFx2
10uFx2
10uFx2
10uFx2
100pF
100pF
100pF
100pF
200pF
200pF
175K
175K
175K
175K
240K
240K
100pF
100pF
50pF
50pF
20pF
20pF
3K
0.834K
62K
Table 3: BOM selection table II.
Note: To guarantee the bandwidth, if decrease the value of
C2, then R3 must be reduced in proportion to C2, and C3
must be increased in proportion to C2.
E-CMOS Corp. (www.ecmos.com.tw)
Page 9 of 10
3L03N-Rev.P001
EC3292
2A, 18V, Synchronous Step-down DC/DC Converter
Package Information
Dmensions
E-CMOS Corp. (www.ecmos.com.tw)
Page 10 of 10
3L03N-Rev.P001
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