ELM651DA CC/CV Mode 36V step down 5A DC/DC converter

ELM651DA CC/CV Mode 36V step down 5A DC/DC converter
■General description
ELM651DA is a step down switching regulator, which has a built-in 40V P-channel power MOSFET for
delivering output current. ELM651DA is designed to allow for operating a wide supply voltage range from 8V
to 36V and capable of delivering 5A output current.
ELM651DA features programmable CV/CC mode control functions, the CV mode (Constant Voltage) function
to provide a regulated voltage output and the CC mode (Constant Current) function provide a current limitation
function, it is suitable for the DC/DC switching power applications when requested the current limitation
function.
■Features
■Application
•
•
•
•
•
•
•
•
•
•
•
• Car charger
• Portable charger applications
• DC/DC converters with current limited
CC/CV mode control
Soft start function for start-up
Output over-voltage protection
Fold back short-circuit protection
High efficiency operation
Input voltage range
Input voltage surge
Fixed operating frequency
Voltage reference accuracy
Current limit accuracy
Package
: 8V to 36V
: 40V
: 80kHz
: ±1%
: ±4%
: SOP-8
■Maximum absolute ratings
Parameter
VCC to GND
LX to VCC
VSEN to GND
ISEN+ to GND
ISEN- to GND
OVP to GND
COMP to GND
Output current
Power dissipation at Ta <60 °C
Operationg temperature
Storage temperature range
Symbol
Vcc
LX
Vsen
ISEN+
ISENOVP
COMP
Icc
Pd
Top
Tstg
Limit
-0.3 to +40.0
+0.3 to -40.0
-0.3 to +7.0
-0.3 to +7.0
-0.3 to +7.0
-0.3 to +7.0
-0.3 to +7.0
6
1
-40 to +85
-60 to 150
Caution:Permanent damage to the device may occur when ratings above maximum absolute ones are used.
Unit
V
V
V
V
V
V
V
A
W
°C
°C
■Selection guide
ELM651DA-N
Symbol
a
b
c
Package
Product version
Taping direction
D: SOP-8
A
N: Refer to PKG file
ELM651DA - N
↑↑ ↑
ab c
* Taping direction is one way.
10 - 1
Rev.1.2
ELM651DA CC/CV Mode 36V step down 5A DC/DC converter
■Pin configuration
SOP-8(TOP VIEW)
1
8
2
7
3
6
4
5
Pin No.
1
2
3
4
5
6
7
8
Pin name
GND
VSEN
ISENISEN+
LX
VCC
OVP
COMP
Pin description
GND
The voltage sense input
The current sense negative input
The current sense positive input
Regulator output
The input supply voltage
The over-voltage sense input
The E/A output pin for frequency compensation
■Block diagram
COMP
8
OVP
LX
VCC
7
6
1.18V
5
Reference
Generator
+
OTP
RAMP
1.18V
+
Error
+ Amp.
-
-
Control
logic
PWM
Comp.
Gate
DRV
Soft start
+
Current
Amp.
0.4V
-
-
+
Vss
1
2
3
4
GND
VSEN
ISEN-
ISEN+
10 - 2
Rev.1.2
ELM651DA CC/CV Mode 36V step down 5A DC/DC converter
■Standard circuit
U1
6
Vin
7
+
C1
8
R1
C3
1
C4
VCC
LX
OVP
ISEN+
COMP ISENGND
L1
5
4
3
D1A
VSEN 2
R2
+
C2
Vout
C5
R3
R5
R4
R6
ELM651DA
GND
■Functional descriptions
1. CV/CC mode control
ELM651DA provides CV/CC function. The CV (constant voltage) function is implemented to deliver a regulated output voltage for the output terminal, and the CC (constant current) function is to limit output current to
be a limited value to prevent the device damaged due to output short circuit or over current condition.
2. Soft start function
ELM651DA is composed of built-in internal soft start function to prevent a large surge current happening
when during start-up period due to the surge current charging output filter capacitors.
3. Output over-voltage protection
ELM651DA provides output over-voltage protection function. When output over-voltage happens, ELM651DA
shuts down and recovers to normal state automatically if output over-voltage is released.
4. Output short-circuit protection
ELM651DA provides output short-circuit protection function. When output short-circuit happens, ELM651DA
shuts down and recovers to normal state automatically if output short-circuit is released.
■Marking
SOP-8
Mark
651
a to o
10 - 3
Content
Product No.code:ELM651DA
Assembly lot No.
Rev.1.2
ELM651DA CC/CV Mode 36V step down 5A DC/DC converter
■Electrical characteristics
Vin=12V, Iout=2.0A, Top=25°C, unless otherwise specified
Condition
Min.
Typ.
Max. Unit
Parameter
Symbol
Input voltage section
Input voltage
Vin
Input no load current
Ino-load Iout=0A
Oscillator section
Operating frequency
Fosc
Duty cycle range
Duty
Error amplifier section
Reference voltage of
Vvsen
the voltage error amplifier
Reference voltage of
Visen
the current error amplifier
Tran conductance of
Gmerr
error amplifier
Output over voltage protection section
Reference voltage of
Vovp
the over voltage comparator
Output short circuit protection section
Reference voltage of the
Vscp
short circuit fold back comparator
MOSFET section
Drain-source breakdown voltage
V(br)dss Vgs=0V, Iout=250µA
Drain-source on-state resistance
Rds (on) Vin=24V, Iout=1A
8
36
10
V
mA
72
80
88
100
kHz
%
1.168
1.180
1.192
V
107.5
112.0
116.5
mV
150
1.145
1.180
µA/V
1.215
0.3
V
V
-40
V
mΩ
90
■Application circuits
U1
L1
Vin
6
7
GND
8
1
R1
+
C1
+
C3
C2 C10 C4 C5
VCC
OVP
LX
ISEN+
COMP ISENGND
L2
5
R5
R3
4
C8
R4
3
1
R6
R8
R7
R9
3
R10
L3 2
Vout+
4
Vout-
LED
VSEN 2
ELM651DA
R2
C6
D1
C9
+
C7
L4
10 - 4
Rev.1.2
ELM651DA CC/CV Mode 36V step down 5A DC/DC converter
BOM List for ELM651DA
Device
C1
C2
C3
C4
C5
C6
C7
C8
C9
C10
D1
L1
L2
L3
L4
LED
R1
R2
R3
R4
R5
R6
R7
R8
R9
R10
U1
Description
Input ECAP, 47µF/35V, 6.3*7mm
Input ECAP, 100µF/35V, 6.3*7mm
MLCC, 0603, X7R
MLCC, 0603, X7R
MLCC, 0603, NPO
MLCC, 0805, X7R
Output ECAP, 220µF/6.3V, 6.3φ*7mm
MLCC, 0603, X7R
MLCC, 0603, X7R
MLCC, 0603, X7R
Schottky diode, SMB, 40V/5A
DR Choke, 4φ*6mm
Power inductor, T- 5052B, L= 100µH wire=0.65
T Core, 6*3*3, 0.5φ*2C*3Ts
SMD bead core , 0805, 220Ω 3000mA
LED, GREEN
Chip R , 0603 , 5%
Chip R , 0805 , 5%
Chip R , 0603 , 5%
Chip R , 0603 , 5%
Chip R , 1206 , 1%
Chip R , 0603 , 1%
Chip R , 0603 , 1%
Chip R , 0603 , 5%
Chip R , 0603 , 5%
Chip R , 0603 , 5%
Buck controller, CC/CV function, Vin 8~36V, SOP-8
Value
47µF/35V
100µF/35V
104
473
47pF
102
220µF/6.3V
NA
104
104
SB54
15µH
100µH
22µH
BEAD
LED
100K
10R
51R
51R
0.045R
390K
118K
470R
120R
1K
ELM651DA
Q'ty
1
1
1
1
1
1
1
0
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
■Application notes
1. Output voltage setting
Figure 1 shows the connections for setting the output voltage value. Typically, selecting the proper ratio of the
two feedback resistors Rvsen1 and Rvsen2 by using Rvsen2 ≈ 118kΩ and determining Vsen from the following
equation: Rvsen1 = Rvsen2 ( Vout / 1.18V - 1 )
Vout
R Vsen1
ELM651DA
Vsen
R Vsen2
Fig-1: Output voltage setting
10 - 5
Rev.1.2
ELM651DA CC/CV Mode 36V step down 5A DC/DC converter
2. CC current setting
The constant current value of ELM651DA is set by a Rs resistor which is connected between Isen+ and Isenpin. The output current of CC mode and Rs resistor are set by the following equation: Rs = 0.112 / ICC
Rs
ELM651DA
Icc
Vout
Isen+
Isen-
Fig-2 : Constant current mode setting
When output voltage is set over 6V, the voltage of the V(Isen+), V(Isen-) should be set under 6V by the following equation: Visen± = (1/ks) Vout ≤ 6V, ks = (Rs1 + Rs2) / Rs2 = (Rs3 + Rs4) / Rs4
Also ks = (Rs1 + Rs2) / Rs2, and Rs = ks × 0.112/Icc at this time.
Rs
Rs1
Isen+
IsenRs2
Vout
Rs3
Rs4
Fig-3 : Constant current mode setting ( At Vout ≥ 6V )
3. Input capacitor selection
The bulk input capacitor selection is based on the voltage rating, the RMS current carrying capability, and the
required input voltage ripple.
The capacitor voltage rating is recommended with 1.5 times for the maximum input voltage as conservative
guideline, depending on the application condition.
The capacitor RMS current rating is considered for stress condition, and the trapezoid current waveform as the
simplified formula is described:
Irms = Iout(max) * √ ( Vout / Vin )
Vin = input voltage ; Vout = output voltage ; Iout(max) = maximum output current.
The capacitor values with respect to the required input voltage ripple if neglect ESR is described:
C = Iout(max) * ΔT / ΔV
ΔT = capacitor supplied charging time ; ΔV = allowable input voltage ripple.
10 - 6
Rev.1.2
ELM651DA CC/CV Mode 36V step down 5A DC/DC converter
4. Output rectifier selection
The output rectifier is selected by the consideration of the reverse voltage rating, the current rating’ and the reverse recovery time and forward voltage drop for the power loss.
The reverse voltage rating should be at least 1.25 times the maximum input voltage for the consideration of
voltage arc.
The current rating should be larger than the maximum inductor current.
The diode conduction loss is due to the forward conduction and is described:
Pcond = Iout(max) * Vf * ( 1 - Vout / Vin )
Vin = input voltage ; Vout = output voltage ; Iout(max) = maximum output current ;
Vf = diode forward voltage.
The diode reverse recovery loss is due to the reverse recovery from the forward conduction to the reverse
blocking state, and is described:
Prr = Qrr * Vin / Tsw
Vin = input voltage ; Qrr = diode reverse recovery charge ; Tsw = switching period.
5. Output inductor selection
The output inductor is selected for the trade-offs between the output inductor current ripple, dc resistance for
power loss, load transient response time, and the physical size.
The output inductor current ripple determines the output voltage ripple requirement, and the inductor’s dc resistance concerns the power loss. The larger the inductor value, the smaller the inductor ripple current, but the
slower the transient response time, the larger the inductor dc resistance, and hence the larger the power loss.
The inductance value is described:
L = Vout * ( 1 - Vout / Vin ) * Tsw / ΔLl
Vin = input voltage ; Vout = output voltage ;
Tsw = switching period ; ΔLl = inductor ripple current.
6. Output capacitor selection
The output capacitor is selected for the trade-offs between output ripple voltage requirement, the output voltage rating, the RMS current rating, the ESR and ESL for the load transient, and the physical size.
The capacitor voltage rating is recommended with 1.5 times for the maximum output voltage as conservative
guideline.
The capacitor RMS current rating is considered for stress condition’ and the trapezoid current waveform as the
simplified formula is described:
Irms = ΔIL / 2√3 ; ΔIL = inductor ripple current.
The output ripple voltage with respect to the capacitor ESR is described:
ΔV = ΔI * ( ESR + Tsw / ( 8 * C ) )
ΔI = capacitor ripple current’ which is equivalent to the inductor ripple current ;
ESR = capacitor equivalent series resistance ; Tsw = switching period.
7. PC board layout consideration
Good PC Board layout is very important in switching converter design. If designed improperly, the PC Board
could radiate excessive noise and contribute to the converter instability.
10 - 7
Rev.1.2
ELM651DA CC/CV Mode 36V step down 5A DC/DC converter
Follows below PC board layout guidelines could get better performance:
1) Path A :
The Vout- is returned to input bulk capacitor C2, by passing through output capacitor C7.
2) Path B :
The output rectifier D1, together with Snubber R2 and C2, are shunt to common ground and returned to input
bulk capacitor C2.
3) Path C and D :
The decoupling capacitor C11, the compensation network R1, C4, C5, the voltage feedback network R6, R7,
C8, and the overvoltage sensing network R8, R9, are connected to IC ground, and returned to input bulk capacitor C2 and output capacitor C7.
4) Path E :
Input capacitor C2 is returned to input ground, after all ground networks are following the above paths designed.
Fig-4 : PC board layout guidelines
U1
L1
Vin
6
7
GND
8
R1
C11 C4 C5
+
+
C1 C3 C2
VCC
LX
OVP
ISEN+
ELM651DA
COMP ISEN-
R5
R3
4
C8
R6
LED
1 Vout+
2
4
C9
R11
R12
2
R13
R15
3
R7
C
1
D1
R2
D
R8
1
R10
3
R14
VSEN 2
GND
C
USB
L3
R4
3
C6
E
L2
5
B
L4
C10 +
4 Vout-
R9
C7
D
A
Fig-5 : The PCB layout of car charger with ELM651DA controller
10 - 8
Rev.1.2
ELM651DA CC/CV Mode 36V step down 5A DC/DC converter
■Typical characteristics
• Vout=5V : Cin=47µF, Cout=220µF, L=100µH, R1=100kΩ, R2=0.025Ω, R3=390kΩ
R4=118kΩ, R5=470Ω, R6=120Ω, C3=0.047µF, C4=47pF, Top=25°C
Current Reference-Top
116
Current Reference-Vin
116
Iload=short
Vin=12V
115
Visen (mV)
Visen (mV)
114
112
Vin=24V
110
Iload=short
113
112
111
-30
1.20
1.19
30
0
Top (�)
60
5
90
Voltage Reference-Top
Vin=24V
Vin (V)
25
30
35
1.190
Iload=1A
1.185
Vin=12V
1.180
1.16
-30
20
1.195
1.18
1.17
15
Voltage Reference-Vin
1.200
Iload=1A
10
Vref (V)
Vref (V)
114
1.175
0
30
Top (�)
60
90
5
10 - 9
10
15
20
Vin (V)
25
30
35
Rev.1.2
ELM651DA CC/CV Mode 36V step down 5A DC/DC converter
EFFICIENCY-Iout
6
Vin=12V
80
Vout-Iout
Vin=12V
5
4
60
Vout (V)
EFFICIENCY (%)
100
Vin=24V
40
20
Vin=24V
3
2
1
0
0.001
0.01
0.1
1
0
0.001
10
Iout (A)
0.01
0.1
Iout (A)
1
10
Frequency-Vin
80.0
79.8
Frequency (kHz)
79.6
79.4
79.2
79.0
Iload=1A
78.8
78.6
78.4
78.2
5
10
15
20
Vin (V)
25
30
35
10 - 10
Rev.1.2