R1270S Series
AEC-Q100 Compliant
3A, 34V Input PWM/VFM Step Down DC/DC Converter with PLL Synchronization
for Automotive Applications
NO.EC-299-200624
OUTLINE
The R1270S is CMOS-based Step-down DC/DC converter with internal N-channel high side Tr. The ON
resistance of the built-in high-side transistor is 0.10Ω and the R1270S can provide the maximum 3A output
current. Each of the ICs consists of an oscillator, a PWM control circuit, a voltage reference unit, an error
amplifier, a phase compensation circuit, a slope compensation circuit, a soft-start circuit, protection circuits, an
internal voltage regulator, and a switch for bootstrap circuit. The ICs can make up a step-down DC/DC
converter with adding an inductor, resistors, a diode, and capacitors externally. The R1270S is current mode
operating type DC/DC converters without an external current sense resistor, and realizes fast response and
high efficiency. As an output capacitor, a ceramic type capacitor is usable. The internal oscillator frequency is
adjustable over a range of 300kHz to 2400kHz by an external resistor, and also can be synchronized externally
by PLL. The phase compensation is adjustable by using external resistor and capacitor. Thereby optimizations
for the inductor and the capacitor can be done. To improve performance under light load conditions, the
R1270S can select automatically between two modes: the VFM mode when the inductor current is
discontinuous and the PWM mode when the inductor current is continuous. The ripple voltage at VFM mode
is 40mV (Typ.). As for protection, the R1270S has a current limit function to control an inductor peak current
every cycle, a fold-back function to reduce the oscillator frequency under the short circuit, a thermal shutdown
function, an under voltage lockout (UVLO) function, and an over voltage lockout (OVLO) function. Furthermore,
the R1270S can include a latch protection function to cut off the output when the output current reaches the
set current limit for a certain time. That is, the R1270S supports two types of the presence (R1270S001A) or
the absence (R1270S001B) of the latch protection function. The current limit, which is fixed at 4.5A (Typ.), is
adjustable by an external resistor. The soft start time is fixed at 0.4ms (Typ.) internally, but is adjustable by an
external resistor. And, the R1270S has the FLG pin to monitor the overvoltage of the FB pin voltage and the
6V rated pin. When detecting an abnormal voltage, the R1270S outputs a flag. The R1270S is available in
HSOP-18 package.
FEATURES
●
●
●
●
Operating Voltage (Maximum Rating) ············· 3.6V to 34V (36V)
Consumption Current ································· Typ. 18µA (V IN = 12V)
Stand-by Current ········································ Typ. 0µA (V IN = 34V, CE=0V)
Output Voltage ··········································· Externally-adjustable at 0.8V or more
(Max. step down ratio 160ns × fosc)
● Feedback Voltage and Tolerance ··················· 0.8V±1.0%
1
R1270S
NO.EC-299-200624
●
●
●
●
●
●
●
●
●
●
●
●
●
Output Current ··········································· 3A(1)
Operating Frequency ·································· 300kHz to 2.4MHz settable by external resistor
Minimum Off Time ······································ Typ. 120ns
Maximum Duty··········································· Min. 93% (fosc = 300kHz), Min. 67% (fosc = 2400kHz)
UVLO Function Detection Voltage ·················· Typ. 2.6V
OVLO Function Detection Voltage ················ Min. 38V
Soft-start Time ··········································· Internal soft-start time (Typ. 0.4ms), as a lower limit,
Externally-adjustable by using capacitor
High-side Switch Current Limit ······················ Typ. 4.5A, as a upper limit,
Externally-adjustable by using resistor
Thermal Shutdown Function ························· Typ. 160°C
CE Threshold Voltage ································· Typ. 1.0V
Latch Protection Delay Time ························· Typ. 2ms (R1270S001A)
Fold-back Protection ··································· Fold-back for oscillation frequency
Packages ················································· HSOP-18
APPLICATIONS
● Power source for car accessories including car audio equipment, car navigation system, and ETC system.
● Power source for control units including EV inverter and charge control.
SELECTION GUIDE
The latch type protection function is user-selectable.
Product Name
Package
Quantity per Reel
Pb Free
Halogen Free
R1270S001∗-E2-#E
HSOP-18
1,000 pcs
Yes
Yes
∗: Select the presence or absence of the latch type protection function.
A: with Latch type protection function
B: without Latch type protection function
#: Select the quality class.
Operating Temperature Range
(1)
2
Test Temp.
A
−40°C to 125°C
25°C, High
K
−40°C to 125°C
Low, 25°C, High
The output current depends on external components and conditions.
R1270S
NO.EC-299-200624
BLOCK DIAGRAMS
VIN
INT
Thermal Shutdown
3.0V
3.0V
+
-
VIN
CE
OVLO
-
UVLO
+
VIN
Shutdown
Regulator
1.0V
+
+
Low:PWM/VFM auto
High:Fixed PWM
2.9V
-
delay
0.8V
φ
PLLREF
Cmp
Filter
+
-
5.0V
PLLFLTR
+
Set
Pulse
RT
Over/Under Voltage Detection
FB
-
Soft Start
Circuit
BST
Maxduty
Pulse
Shutdown
Reset
SS
VCO
OVP
UVD
S D
LX
OVP
-
+
R
+
Shutdown
UVD
LMTOVP
Limit Latch
Pin OVD
Softstart
Reference
ER
Reset
Limit Latch
Circuit (2 msec) *1
EC
LMT
Set
PLLFLTR
SS
ER
3.3V
*1
Peak Current
Limit Circuit
LMT
OVP
+
Pin OVD
FLG
Reset
Shutdown
Current Sense Circuit
GND
Current Slope Circuit
R1270S001A equips the limit latch circuit.
R1270S001A/B Block Diagram
3
R1270S
NO.EC-299-200624
PIN DESCRIPTIONS
1
LX
2
LX
3
NC
TOP VIEW
VIN
18
VIN
17
BST
16
*
SS
15
PAD
CE
14
4
GND
5
INT
6
FB
FLG
13
7
ER
RT
12
8
EC
PLLFLTR
11
9
LMT
PLLREF
10
R1270S (HSOP-18) Pin Configuration
R1270S Pin Description
Pin No.
Symbol
Description
1, 2
LX
Lx Switching Pin
3
NC
No connection
4
GND
5
INT
Internal Bias Pin
6
FB
Feedback Pin
7
ER
Phase Compensation Pin for External Resistor
8
EC
Phase Compensation Pin for External Capacitor
9
LMT
Current Limit adjustment Pin
10
PLLREF
PLL Synchronization Pin
11
PLLFLTR
PLL Filter Pin
12
RT
13
FLG
Flag Output Pin
14
CE
Chip Enable Pin (Active “H”)
15
SS
Soft-start Pin
16
BST
Bootstrap Pin
17, 18
VIN
Power Supply Pin
Ground Pin
Oscillation adjustment Pin
* The tab on the bottom of the package must be electrically connected to GND (substrate level) when mounted on the
board.
4
R1270S
NO.EC-299-200624
Internal Equivalent Circuit for Each Pin
VIN
VIN
Regulator
INT
LX
VIN
Regulator
FB
VIN
Regulator
ER
VIN
VIN
Regulator
Regulator
Regulator
LMT
EC
5
R1270S
NO.EC-299-200624
Regulator
VIN
VIN
PLLREF
PLLFLTR
Regulator
VIN
FLG
RT
VIN
CE
SS
6
VIN
Regulator
R1270S
NO.EC-299-200624
Regulator
BST
LX
7
R1270S
NO.EC-299-200624
ABSOLUTE MAXIMUM RATINGS
(GND = 0 V)
Symbol
V IN
V BST
V LX
V CE
V INT
V SS
V ER
V EC
V FB
V FLG
V PLLREF
V PLLFLTR
V RT
V LMT
PD
Tj
Tstg
Item
Input Voltage
BST Pin Voltage(1)
LX Pin Voltage
CE Pin Input Voltage
INT Pin Voltage
Soft-start Pin Voltage
ER Pin Voltage
EC Pin Voltage
Feedback Pin Voltage
Flag Pin Voltage(1)
External Oscillation Synchronization Pin Voltage
PLL Filter Pin Voltage
Oscillation adjustment Pin Voltage
Current Limit adjustment Pin Voltage
Power Dissipation(2) (HSOP-18, JEDEC STD.51)
Junction Temperature
Storage Temperature Range
Rating
−0.3 to 36
V LX −0.3 to V LX +6
−0.3 to 36
−0.3 to 36
−0.3 to 36
−0.3 to 6
−0.3 to 6
−0.3 to 6
−0.3 to 6
−0.3 to 24
−0.3 to 36
−0.3 to 6
−0.3 to 6
−0.3 to 6
3900
−40 to 150
−55 to 150
Unit
V
V
V
V
V
V
V
V
V
V
V
V
V
V
mW
°C
°C
ABSOLUTE MAXIMUM RATINGS
Electronic and mechanical stress momentarily exceeded absolute maximum ratings may cause permanent damage
and may degrade the life time and safety for both device and system using the device in the field. The functional
operation at or over these absolute maximum ratings are not assured.
RECOMMENDED OPERATING CONDITIONS
Symbol
V IN
Ta
Item
Input Voltage
Operating Temperature Range
Rating
3.6 to 34
−40 to 125
Unit
V
°C
RECOMMENDED OPERATING CONDITIONS
All of electronic equipment should be designed that the mounted semiconductor devices operate within the
recommended operating conditions. The semiconductor devices cannot operate normally over the recommended
operating conditions, even if they are used over such conditions by momentary electronic noise or surge. And the
semiconductor devices may receive serious damage when they continue to operate over the recommended
operating conditions.
(1)
(2)
8
The pin voltage except VBST and VFLG must be prevented from exceeding VIN +0.3V.
Refer to POWER DISSIPATION for detailed information.
R1270S
NO.EC-299-200624
ELECTRICAL CHARACTERISTICS
V IN = 12 V, Ta = 25°C, unless otherwise specified.
are guaranteed by design engineering at -40°C ≤ Ta ≤ 125°C.
The specifications surrounded by
R1270S001A/B-AE
Symbol
Item
Conditions
Min.
Typ.
0.7
1
1.3
mA
13
18
30
µA
2.5
2.6
2.7
V
V UVLO2
−0.15
V UVLO2
−0.11
V
V UVLO2
UVLO Released Voltage
V IN = 34 V, V INT = Open,
V PLLREF = 34 V, V FB = 1.5 V
V IN = 34 V, V INT = Open,
V PLLREF = 0, V FB = 0.84 V
V IN Rising
V UVLO1
UVLO Detect Voltage
V IN Falling
V UVLO2
−0.16
V OVLO2
OVLO Released Voltage
V IN Falling
34
V OVLO1
OVLO Detect Voltage
V IN Rising
V FB
V FB Voltage Tolerance
V VFM
FB High Detection at VFM mode
fosc0
Oscillation Frequency 0
RT = Open
270
fosc1
Oscillation Frequency 1
RT = 62 kΩ
fosc2
Oscillation Frequency 2
RT = GND
I IN1
V IN Consumption current 1
I IN2
V IN Consumption current 2
toff
(Ta = 25°C)
Max. Unit
V
38
Ta = 25°C
0.792
−40°C ≤ Ta ≤ 125°C
0.784
V
0.808
V
0.816
V
0.831
V
300
330
kHz
900
1010
1120
kHz
2160
2400
2640
kHz
0.800
120
Minimum Off Time
ns
D MAX0
Maximum Duty Cycle 0
RT = Open
93
%
D MAX0
Maximum Duty Cycle 1
RT = 62 kΩ
83
%
D MAX2
RT = GND
67
%
tss1
Maximum Duty Cycle 2
Oscillation Synchronized
Frequency
Soft-start Time 1
SS = Open, V FB = 0.72 V
0.3
0.55
ms
tss2
Soft-start Time 2
C SS = 0.01 µF, V FB = 0.72 V
3.1
4.5
ms
Itss
Soft-start charge current
SS = 0 V
1.7
2.0
2.35
µA
Delay Time for Latch Protection
Lx High Side Switch ON
Resistance
Lx High Side Switch Leakage
Current
Lx High Side Switch Limited
Current 1
Lx High Side Switch Limited
Current 2
for R1270S001A
V BST −V LX = 4.5V, I LX =
0.1A
1.4
2
2.8
ms
0.1
0.15
Ω
0
20
µA
f SYNC
tdelay
R LXH
I LXHOFF
I LIMLXH1
I LIMLXH2
f PLLREF = 1000 kHz
fosc/2
foscx2 kHz
LMT = 220 kΩ、DC Current
3.0
3.5
4.3
A
LMT = 39 kΩ、DC Current
1.25
1.6
2.4
A
9
R1270S
NO.EC-299-200624
V IN = 12 V, Ta = 25°C, unless otherwise specified.
are guaranteed by design engineering at -40°C ≤ Ta ≤ 125°C.
The specifications surrounded by
R1270S001A/B-AE (Continued)
Symbol
Item
Conditions
Min.
V CEH
CE “H” Input Voltage
V CEL
CE “L” Input Voltage
I CEH
CE “H” Input Current
−1.0
I CEL
CE “L” Input Current
I FBH
FB “H” Input Current
I FBL
FB “L” Input Current
1.15
V
0
1.0
µA
−1.0
0
1.0
µA
V FB = 1.5 V
−0.1
0
0.1
µA
V FB = 0 V
−0.1
0
0.1
µA
PLLREF “H” Input Voltage
V PLLL
PLLREF “L” Input Voltage
I PLLH
PLLREF“H” Input Current
−1.0
PLLREF“L” Input Current
Thermal Shutdown Detect
Temperature
Thermal Shutdown Release
Temperature
Standby Current
−1.0
V IN = 34 V, V CE = 0 V
V FLGL
FLAG ”L” Voltage
V IN = 2.0 V, I FLG = 1 mA
I FLGOFF
FLAG ”Off” Current
V FLG = 6.0 V
T TSD
T TSR
Istandby
V
0.85
V PLLH
I PLLL
Typ.
(Ta = 25°C)
Max. Unit
0.95
V
0.67
V
0
1.0
µA
0
1.0
µA
160
°C
130
°C
0
20
µA
0.25
V
0.0
0.1
µA
V OVP
FB Pin OVP Detect Voltage
0.91
0.98
1.04
V
V UVD
FB Pin UVD Detect Voltage
0.59
0.64
0.69
V
V FLB
0.59
0.69
V
V VOS0
Fold Back Detect Voltage
6V-rated Pin OVP Detect
Voltage
INT Pin Operation Voltage
V VOS1
INT Pin Disable Voltage
V POVD
4.0
V ER , V PLLFLTR , V SS
V
2.75
3.1
V
2.68
2.8
V
All test items listed under Electrical Characteristics are done under the pulse load condition (Tj ≈ Ta = 25°C).
10
R1270S
NO.EC-299-200624
V IN = 12 V, unless otherwise specified.
R1270S001A/B-KE
Symbol
Item
Min.
0.7
1
1.3
mA
13
18
30
µA
2.5
2.6
2.7
V
V UVLO2
−0.16
34
V UVLO2
−0.15
V UVLO2
−0.11
V
V UVLO2
UVLO Released Voltage
V IN = 34 V, V INT = Open,
V PLLREF = 34 V, V FB = 1.5 V
V IN = 34 V, V INT = Open,
V PLLREF = 0, V FB = 0.84 V
V IN Rising
V UVLO1
UVLO Detect Voltage
V IN Falling
V OVLO2
OVLO Released Voltage
V IN Falling
V OVLO1
OVLO Detect Voltage
V IN Rising
V FB
V FB Voltage Tolerance
V VFM
FB High Detection at VFM mode
fosc0
Oscillation Frequency 0
RT = Open
270
fosc1
Oscillation Frequency 1
RT = 62 kΩ
fosc2
Oscillation Frequency 2
RT = GND
I IN1
V IN Consumption current 1
I IN2
V IN Consumption current 2
toff
(−40°C ≤ Ta ≤ 125°C)
Typ.
Max. Unit
Conditions
V
38
Ta = 25°C
0.792
−40°C ≤ Ta ≤ 125°C
0.784
V
0.808
V
0.816
V
0.831
V
300
330
kHz
900
1010
1120
kHz
2160
2400
2640
kHz
0.800
120
Minimum Off Time
ns
D MAX0
Maximum Duty Cycle 0
RT = Open
93
%
D MAX0
Maximum Duty Cycle 1
RT = 62 kΩ
83
%
D MAX2
RT = GND
67
%
tss1
Maximum Duty Cycle 2
Oscillation Synchronized
Frequency
Soft-start Time 1
SS = Open, V FB = 0.72 V
0.3
0.55
ms
tss2
Soft-start Time 2
C SS = 0.01 µF, V FB = 0.72 V
3.1
4.5
ms
Itss
Soft-start charge current
SS = 0 V
1.7
2.0
2.35
µA
Delay Time for Latch Protection
Lx High Side Switch ON
Resistance
Lx High Side Switch Leakage
Current
Lx High Side Switch Limited
Current 1
Lx High Side Switch Limited
Current 2
for R1270S001A
V BST −V LX = 4.5V, I LX =
0.1A
1.4
2
2.8
ms
0.1
0.15
Ω
0
20
µA
f SYNC
tdelay
R LXH
I LXHOFF
I LIMLXH1
I LIMLXH2
f PLLREF = 1000 kHz
fosc/2
foscx2 kHz
LMT = 220 kΩ、DC Current
3.0
3.5
4.3
A
LMT = 39 kΩ、DC Current
1.25
1.6
2.4
A
11
R1270S
NO.EC-299-200624
V IN = 12 V, unless otherwise specified.
R1270S001A/B-KE (Continued)
Symbol
Item
Conditions
Min.
V CEH
CE “H” Input Voltage
V CEL
CE “L” Input Voltage
I CEH
CE “H” Input Current
−1.0
I CEL
CE “L” Input Current
I FBH
FB “H” Input Current
I FBL
FB “L” Input Current
1.15
V
0
1.0
µA
−1.0
0
1.0
µA
V FB = 1.5 V
−0.1
0
0.1
µA
V FB = 0 V
−0.1
0
0.1
µA
PLLREF “H” Input Voltage
V PLLL
PLLREF “L” Input Voltage
I PLLH
PLLREF“H” Input Current
−1.0
I PLLL
PLLREF“L” Input Current
Thermal Shutdown Detect
Temperature
Thermal Shutdown Release
Temperature
Standby Current
−1.0
V IN = 34 V, V CE = 0 V
V FLGL
FLAG ”L” Voltage
V IN = 2.0 V, I FLG = 1 mA
I FLGOFF
FLAG ”Off” Current
V FLG = 6.0 V
T TSR
Istandby
0.95
V
0.67
V
0
1.0
µA
0
1.0
µA
160
°C
130
°C
0
20
µA
0.25
V
0.0
0.1
µA
V OVP
FB Pin OVP Detect Voltage
0.91
0.98
1.04
V
V UVD
FB Pin UVD Detect Voltage
0.59
0.64
0.69
V
V FLB
0.59
0.69
V
V VOS0
Fold Back Detect Voltage
6V-rated Pin OVP Detect
Voltage
INT Pin Operation Voltage
V VOS1
INT Pin Disable Voltage
V POVD
12
V
0.85
V PLLH
T TSD
(−40°C ≤ Ta ≤ 125°C)
Typ.
Max. Unit
4.0
V ER , V PLLFLTR , V SS
V
2.75
3.1
V
2.68
2.8
V
R1270S
NO.EC-299-200624
THEORY OF OPERATION
OVLO (Over Voltage Lock Out) Function
When the input voltage to V IN pin is higher than OVLO detection voltage, the inside circuit becomes standby
to prevent malfunction. If the voltage on the V IN pin becomes lower than the OVLO release voltage, R1270S
will restart and the soft-start function will begin. Also, the OVLO protection has a function to prevent the
possibility of the malfunction and destruction to the IC. Since the OVLO detection voltage is set higher than
the absolute maximum rating for V IN pin, the function itself is not guaranteed.
OVP (Over Voltage Protection) Function for FB Pin
When the FB pin voltage becomes higher than the OVP detection voltage, the OVP function stops the switching
of Lx pin without stopping the function of the internal circuit. When the FB pin voltage becomes lower than the
OVP detect voltage, the Lx pin switching returns to normal control. If aberrant conditions around the FB pin
circuit occur, the overvoltage of the output voltage may not be decreased because the R1270S indirectly
monitors the output voltage via FB pin.
Setup for Oscillation Frequency
By using R RT between the RT pin and GND, the R1270S can control the oscillation frequency in the range of
300 kHz to 2400 kHz. For example, by using 62 kΩ as R RT , the frequency will be set about 1000 kHz.
When setting the frequency at either 300 kHz or 2400 kHz, the frequency depends on whether the RT pin is
set to "Open" or "GND", without using RRT. That is, the frequency is set at 300 kHz when the RT pin is “Open”,
and is set at 2400 kHz when it is “GND”.
The Electrical Characteristics guarantees the oscillation frequency under the conditions stated below for f OCS0 ,
f OCS1 and f OCS2 .
3000
fOSC [kHz]
2500
2000
1500
1000
500
0
0
50
100
150
200
250
300
RRT[kΩ]
R RT [kΩ] = 1 / (1 / (((1 / fosc [kHz] x 1000000 −125) / 292 x 25) − 25) − 1 / 250)
R1270S001A/B Oscillation Frequency Setting Resistor (R RT ) vs. Oscillation Frequency (fosc)
13
R1270S
NO.EC-299-200624
Synchronization of Oscillation Frequency
The R1270S can synchronize to an external clock, which is input from the PLLREF pin, with using phaselocked loop. The PWM fixed mode is set during synchronization. The detection threshold of the external clock
is 0.8 V (Typ.) and the pulse of 100 ns or more are required.
The phase compensation filter is required to stabilize the phase-locked loop. The frequency fluctuation, which
is changed from the set frequency to the synchronized frequency, can be achieved smoothly by the constant
of this filter. Place 10 kΩ resistor and 220 pF capacitor in series between PLLFTR pin and GND.
The oscillation frequency which could be synchronized is 0.5 to 2 times of that stated in the “Setup of Oscillation
Frequency”. However the guaranteed oscillation frequency is 270 kHz at the minimum, and 2640 kHz at the
maximum. Until the soft-start sequence is over, the R1270S operates at set oscillation frequency and after the
soft-start sequence is over the oscillation frequency is synchronized to the external clock.
The phase compensation filter is charged with limited impedance, and the filter must be charged when
synchronization starts. The time required for the phase compensation filter to be charged is as bellow.
POLE PLL : 1/(C PLL *(R PLL +260k))
95% charged : 3/POLE PLL [sec]
98% charged : 4/POLE PLL [sec]
Adjust the soft-start time or the timing of the external clock input as POLE PLL. The following shows the timing
chart of self oscillation and external clock input.
VOUT
VCPLL
PLLREF
fosc
R1270S001A/B PLL Filter Start-up Sequence
Phase Compensation Filter Charging Time > Soft-Start Time
14
R1270S
NO.EC-299-200624
VOUT
VCPLL
PLLREF
fosc
R1270S001A/B PLL Filter Start-up Sequence
Phase Compensation Filter Charging Time < Soft-Start Time
VOUT
VCPLL
PLLREF
fosc
R1270S001A/B PLL Filter Start-up Sequence
Phase Compensation Filter Charging Time < Synchronous Start Time with Eternal Clock
VFM/PWM Alternative Mode and PWM Fixed Mode
By applying either the voltage of 0.95 V or more or the external clock to the PLLREF pin, the R1270S operates
in PWM fixed mode (Pulse-skip at light load). By applying the voltage of 0.67 V or less to the PLLREF pin, the
R1270S operates in VFM/PWM alternative mode.
INT Pin Voltage
By applying the voltage of 3.1 V (Typ.) or more to the INT pin via the V OUT pin, the R1270S generates 3 V
internal power supply from V OUT. Thereby the R1270S can improve the efficiency of the IC in VFM mode. When
I IN_VFM is as the 3 V internal current supply, the approximate expression for IC’s consumption current: I IN is
V OUT / V IN × I IN_VFM . That is, the consumption current will decrease as V OUT /V IN becomes smaller. But, when
the INT pin voltage is lower than 3.1 V, the consumption current will not be reduced since the internal voltage
supply becomes V IN . Therefore, this architecture is aimed for applications which the V OUT is 3.3 V or more.
If the V OUT is lower than 3.3 V, set the INT pin OPEN (No C INT necessary).
15
R1270S
NO.EC-299-200624
Minimum ON Time
The minimum ON time is 160ns that is determined by the current sense circuit.
The R1270S adopts a resistor free current control mode. By using R ON (Nch driver ON resistor) as a substitute
for sense resistor, the R1270S senses I LX (inductor current) according to V IN − V LX = I LX x R ON. The R1270S
can sense I LX only during the Nch driver is On (Lx = “High”). However, if sensing it during the occurrence of
the surge current right after the driver turns On, a malfunction may occur. To avoid the malfunction, the R1270S
maintains a none sensing time for a while after the driver turns On.
If the current control mode and the current limit circuit will not function properly at none sensing time, the
R1270S may result in a rapid deterioration of stability and current limit accuracy. Please select the output
voltage settings and frequency settings so that the output voltage does not become lower than the minimum
step down ratio V IN ×160ns×f OCS .
C SPD Setting
The transfer function from feedback resistor of V OUT to FB pin using C SPD is
V OUT /FB[s] = (R TOP ×R BOT ×C SPD ×s+R BOT ) / (R TOP ×R BOT ×C SPD ×s+R TOP +R BOT )
From above equation, the zero is R BOT /(R TOP ×R BOT ×C SPD ) and the pole is (R TOP +R BOT )/(R TOP ×R BOT ×C SPD ).
At low frequency level below zero V OUT will be multiplication of R BOT /(R TOP +R BOT ) which means feedback by
0.8/V OUT and when higher frequency level than the pole it will be feedback by 1.
At VFM mode the ripple of V OUT is generated by 40mV (Typ.) higher than that of the reference voltage at PWM
mode which is 0.8V. For all operating frequency range, the ripple of V OUT is feedback by 1 to the FB pin despite
the output voltage settings ripple of V OUT will follow reference voltage by setting the C SPD large. The bellow
shows the example of setting the C SPD large, where the ripple of V OUT is feedback by 1 to the FB pin, and
setting the C SPD small, where the ripple of V OUT is feedback by the multiple of R BOT / (R TOP +R BOT ).
FB pin Voltage
40mV
0.8V
40mV x (RTOP + RBOT) /RBOT
VOUT (CSPD Small)
VOUT (CSPD Large)
40mV
0.8V x (RTOP + RBOT) /RBOT
R1270S001A/B VFM Ripple FB vs. V OUT
As shown in the above figure, the ripple of V OUT becomes larger when the C SPD is small.
16
R1270S
NO.EC-299-200624
The recommended C SPD value is selected to minimize the ripple of V OUT . When changing the R BOT value from
the recommended value, please make sure the R BOT ×C SPD is also in the range of the recommended value and
change the C SPD together. Also, changing L, C OUT , R ER , C EC from the recommended value is required to
change the C SPD .
Furthermore, if the ripple of the VOUT is permissible, improving the loop stability is possible by adjusting the
positive bump of the zero and pole. First, measure the voltage drop of the output by the load transient response
without C SPD . Then measure the voltage drop again with attachment of small enough C SPD . If the selected
C SPD is too small, the amount of the voltage drop will be the same value as the value without C SPD . Repeat the
procedure with increasing C SPD value gradually. When the voltage drop begins to improve, suppose that value
as C SPD1 . Further try other C SPD value by increasing it gradually, then the voltage drop improvement will stop.
Suppose that the C SPD value as Cspd2. The appropriate C SPD value can be calculated as the next formula;
C SPD =√(C SPD1 ×C SPD2 ). The zero will be low and pole will be high of the feedback resistor at the whole
frequency range, the ripple at VFM mode will be lower than that V OUT (C SPD small) of above diagram
FLAG Output Function
The R1270S has an Nch open drain FLAG output. When abnormality is detected, the R1270S switches the
Nch transistor On, and sets the FLG pin to “Low”. When the abnormality is removed, the R1270S switches the
Nch transistor Off and sets the FLG pin to “High” (V FLGIN ). The UVD will function only when V FB 1A
3.7
3.3
3.1
Output Current
2
1
0
0
42
0.02
0.04
time [ms]
0.06
0.08
Output Voltage
3.5
3.3
2
Output Current
1
0
0
0.1
0.2
time [s]
0.3
0.4
Output Current [A]
3.5
Output Voltage [V]
Output Voltage
Output Current [A]
Output Voltage [V]
3.7
R1270S
NO.EC-299-200624
fosc = 1000 kHz
fosc = 1000kHz / VOUT = 3.3V / VFM PWM
VIN = 12V / IOUT = 3A -> 1A
fosc = 1000kHz / VOUT = 3.3V / VFM PWM
VIN = 12V / IOUT = 1A -> 3A
3.6
3.3
3.2
Output Current
3
1.5
0
0
0.04
0.08
time [ms]
0.12
3.5
Output Voltage
3.4
3.3
3
Output Current
1.5
0
0.16
0
0.04
0.08
time [ms]
0.12
Output Current [A]
3.4
Output Voltage [V]
Output Voltage
3.5
Output Current [A]
Output Voltage [V]
3.6
0.16
fosc = 2000 kHz
fosc = 2000kHz / VOUT = 5.0V / VFM PWM
VIN = 12V / IOUT = 1A -> 0A
fosc = 2000kHz / VOUT = 5.0V / VFM PWM
VIN = 12V / IOUT = 0A -> 1A
Output Current
1
0
0
0.04
0.08
time [ms]
0.12
Output Voltage [V]
5
Output Current [A]
5.1
5
0
0.16
0
0.1
0.2
time [s]
0.3
0.4
fosc = 2000kHz / VOUT = 5.0V / VFM PWM
VIN = 12V / IOUT = 3A -> 1A
fosc = 2000kHz / VOUT = 5.0V / VFM PWM
VIN = 12V / IOUT = 1A -> 3A
5.5
5.25
Output Voltage
5
4.75
3
Output Current
1.5
0
0
0.02
0.04
time [ms]
0.06
0.08
Output Voltage [V]
5.5
Output Current [A]
Output Voltage [V]
1
Output Current
Output Voltage
5.25
5
3
Output Current
1.5
0
0
0.02
0.04
time [ms]
0.06
Output Current [A]
Output Voltage [V]
5.1
4.9
Output Voltage
5.2
Output Current [A]
Output Voltage
5.2
0.08
43
R1270S
NO.EC-299-200624
21) Output Current Vs. Output Voltage
fosc = 300 kHz
fosc = 1000 kHz
fosc = 300kHz / VOUT = 3.3V
VIN = 12V
3.5
( Ta = 25°C)
3.35
3.3
3.25
12V VFMPWM
3.2
12V PWM
Output Voltage [V]
Output Voltage [V]
3.4
3.15
3.4
3.35
3.3
3.25
12V VFMPWM
3.2
12V PWM
3.15
3.1
3.1
0
1000
2000
3000
Output Current [mA]
4000
fosc = 2000 kHz
fosc = 2000kHz / VOUT = 5.0V
VIN = 12V
5.3
Output Voltage [V]
( Ta = 25°C)
3.45
3.45
( Ta = 25°C)
5.2
5.1
5
4.9
12V VFMPWM
4.8
12V PWM
4.7
0
44
fosc = 1000kHz / VOUT = 3.3V
VIN = 12V
3.5
1000
2000
3000
Output Current [mA]
4000
0
1000
2000
3000
Output Current [mA]
4000
R1270S
NO.EC-299-200624
22) Input Transient Response
fosc = 300 kHz
fosc = 300kHz / VOUT = 3.3V / VFM PWM
VIN = 8V 16V / IOUT = 0.1A
fosc = 300kHz / VOUT = 3.3V / VFM PWM
VIN = 8V 16V / IOUT = 1.5A
Output Voltage
3.5
3.3
Input Voltage
16
8
0
0
2
4
time [ms]
6
3.4
Output Voltage
3.35
3.3
3.25
Input Voltage
3.2
3.15
16
3.1
8
3.05
0
8
0
2
4
time [ms]
6
Input Voltage [V]
3.7
Output Voltage [V]
3.45
Input Voltage [V]
Output Voltage [V]
3.9
8
fosc = 1000 kHz
fosc = 1000kHz / VOUT = 3.3V / VFM PWM
VIN = 8V 16V / IOUT = 1.5A
fosc = 1000kHz / VOUT = 3.3V / VFM PWM
VIN = 8V 16V / IOUT = 0.1A
3.45
Output Voltage
3.5
3.3
Input Voltage
16
8
0
0
4
2
time [ms]
6
3.4
Output Voltage
3.35
3.3
3.25
Input Voltage
16
8
0
0
8
2
4
time [ms]
6
Input Voltage [V]
Output Voltage [V]
3.7
Input Voltage [V]
Output Voltage [V]
3.9
8
fosc = 2000 kHz
fosc = 2000kHz / VOUT = 5.0V / VFM PWM
VIN = 8V 16V / IOUT = 1.5A
fosc = 2000kHz / VOUT = 5.0V / VFM PWM
VIN = 8V 16V / IOUT = 0.1A
5.1
Output Voltage [V]
Output Voltage
5.2
5
16
8
0
2
4
time [ms]
5
4.95
Input Voltage
Input Voltage
0
Output Voltage
5.05
6
8
16
8
0
0
2
4
time [ms]
6
Input Voltage [V]
5.4
Input Voltage [V]
Output Voltage [V]
5.6
8
45
R1270S
NO.EC-299-200624
23) Input Voltage Vs. Output Voltage
fosc = 300 kHz
fosc = 300kHz / VOUT = 3.3V / VFM PWM
fosc = 300kHz / VOUT = 3.3V / PWM
3.4
( IOUT )
0mA
1mA
10mA
100mA
1A
3A
3.36
3.34
3.32
3.3
3.28
3.26
( IOUT )
3.38
0mA
1mA
10mA
100mA
1A
3A
3.36
Output Voltage [V]
3.38
Output Voltage [V]
3.4
3.34
3.32
3.3
3.28
3.26
3.24
3.24
3.22
3.22
3.2
3.2
0
10
20
Input Voltage [V]
30
0
10
20
Input Voltage [V]
30
fosc = 1000 kHz
fosc = 1000kHz / VOUT = 3.3V / VFM PWM
fosc = 1000kHz / VOUT = 3.3V / PWM
3.4
3.34
3.32
3.3
3.28
3.26
Output Voltage [V]
0mA
1mA
10mA
100mA
1A
3A
3.36
Output Voltage [V]
3.4
( IOUT )
3.38
0mA
3.36
1mA
3.34
10mA
3.32
100mA
3.3
1A
3.28
3A
3.26
3.24
3.24
3.22
3.22
3.2
( IOUT )
3.38
3.2
0
10
20
Input Voltage [V]
30
0
10
20
Input Voltage [V]
30
fosc = 2000 kHz
fosc = 2000kHz / VOUT = 5.0V / PWM
fosc = 2000kHz / VOUT = 5.0V / VFM PWM
5.3
( IOUT )
5.1
5
4.9
( IOUT )
5.08
0mA
1mA
10mA
100mA
1A
3A
5.06
Output Voltage [V]
0mA
1mA
10mA
100mA
1A
3A
5.2
Output Voltage [V]
5.1
5.04
5.02
5
4.98
4.96
4.94
4.8
4.92
4.7
4.9
5
46
15
25
Input Voltage [V]
35
5
15
25
Input Voltage [V]
35
POWER DISSIPATION
HSOP-18
Ver. B
The power dissipation of the package is dependent on PCB material, layout, and environmental conditions.
The following measurement conditions are based on JEDEC STD. 51-7.
Measurement Conditions
Item
Measurement Conditions
Environment
Mounting on Board (Wind Velocity = 0 m/s)
Board Material
Glass Cloth Epoxy Plastic (Four-Layer Board)
Board Dimensions
76.2 mm × 114.3 mm × 0.8 mm
Copper Ratio
Outer Layer (First Layer): Less than 95% of 50 mm Square
Inner Layers (Second and Third Layers): Approx. 100% of 50 mm Square
Outer Layer (Fourth Layer): Approx. 100% of 50 mm Square
Through-holes
φ 0.3 mm × 21 pcs
Measurement Result
(Ta = 25°C, Tjmax = 150°C)
Item
Measurement Result
Power Dissipation
3900 mW
θja = 32°C/W
Thermal Resistance (θja)
Thermal Characterization Parameter (ψjt)
ψjt = 8°C/W
θja: Junction-to-Ambient Thermal Resistance
ψjt: Junction-to-Top Thermal Characterization Parameter
4000
3900
Power Dissipation PD (mW)
3500
3000
2500
2000
1500
1000
500
0
0
25
50
75
100
125
150
Ambient Temperature (°C)
Power Dissipation vs. Ambient Temperature
Measurement Board Pattern
i
PACKAGE DIMENSIONS
HSOP-18
Ver. A
∗
HSOP-18 Package Dimensions
i
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