RY9135
17V 3A 600KHz ECOT Sync Step-Down Regulator
Features
•
•
•
•
Wide 4.5V to 17V Operating Input Range
3A Continuous Output Current
600KHz Switching Frequency
ECOT Mode Control with Fast Transient
Response
•
•
•
•
Built-in Over Current Limit
Built-in Over Voltage Protection
Force-PWM Mode
Internal Soft-Start
•
70mΩ/50mΩ Low RDS(ON) Internal Power
MOSFETs
•
•
•
•
•
•
•
Output Adjustable from 0.765V
No Schottky Diode Required
Short Protection with Hiccup-Mode
Integrated internal compensation
Thermal Shutdown
Available in SOT23-6 Package
-40°C to +85°C Temperature Range
•
•
•
•
Digital Video Recorder (DVR)
Portable Media Player (PMP)
Cable Modem / XDSL
General Purposes
Applications
•
•
•
•
Digital Set-top Box (STB)
Tablet Personal Computer (Pad)
Flat-Panel Television and Monitor
Wi-Fi Router / AP
General Description
The RY9135 is a high frequency, synchronous, rectified, step-down, switch-mode converter with internal power
MOSFETs. It offers a very compact solution to provide a 3A continuous output current over a wide input supply
range, with excellent load and line regulation. ECOT control operation provides very fast transient response and
easy loop design as well as very tight output regulation.
The RY9135 requires a minimal number of readily available, external components and is available in a space saving
SOT23-6 package.
Typical Application Circuit
C1
BS
VIN
IN
L1
VOUT
SW
R1
CIN
ON/
OFF
CFF
COUT
RT Opt.
EN
FB
GND
R2
Basic Application Circuit
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RY9135
17V 3A 600KHz ECOT Sync Step-Down Regulator
Pin Description
Pin Configuration
TOP VIEW
GND
1
6
BS
SW
2
5
EN
IN
3
4
FB
SOT23-6
Top Marking: EGYLL (device code: EG, Y=year code, LL= lot number code)
Pin Description
Pin
Name
Function
1
GND
2
SW
Switching Pin
3
IN
Power Supply Pin
4
FB
Adjustable Version Feedback input. Connect FB to the center point of the external
resistor divider
5
EN
Drive this pin to a logic-high to enable the IC. Drive to a logic-low to disable the
IC and enter micro-power shutdown mode.
6
BS
Bootstrap. A capacitor connected between SW and BS pins is required to form a
floating supply across the high-side switch driver.
Ground Pin
Order Information (1)
Marking
Part No.
Model
Description
Package
T/R Qty
EGYLL
70301343
RY9135
RY9135 ECOT Buck, 4.5-17V, 3A,
600KHz, VFB 0.765V, SOT23-6
SOT23-6
3000PCS
Note (1): All RYCHIP parts are Pb-Free and adhere to the RoHS directive.
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RY9135
17V 3A 600KHz ECOT Sync Step-Down Regulator
Specifications
Absolute Maximum Ratings (1) (2)
Item
Min
Max
Unit
VIN voltage
-0.3
18
V
EN voltage
-0.3
18
V
SW voltage
-0.3
VIN+0.5V
V
BS voltage
-0.3
Vsw+5V
V
–0.3
6
V
FB voltage
Power dissipation
(3)
Internally Limited
Operating junction temperature, TJ
-40
150
°C
Storage temperature, Tstg
–55
150
°C
260
°C
Lead Temperature (Soldering, 10sec.)
Note (1): Exceeding these ratings may damage the device.
Note (2): The device is not guaranteed to function outside of its operating conditions.
Note (3): The maximum allowable power dissipation is a function of the maximum junction temperature, TJ(MAX),
the junction-to-ambient thermal resistance, RθJA, and the ambient temperature, TA. The maximum allowable power
dissipation at any ambient temperature is calculated using: PD (MAX) = (TJ(MAX) − TA)/RθJA. Exceeding the maximum
allowable power dissipation causes excessive die temperature, and the regulator goes into thermal shutdown.
Internal thermal shutdown circuitry protects the device from permanent damage. Thermal shutdown engages at
TJ=160°C (typical) and disengages at TJ= 130°C (typical).
ESD Ratings
Item
Description
Value
Unit
V(ESD-HBM)
Human Body Model (HBM)
ANSI/ESDA/JEDEC JS-001-2014
Classification, Class: 2
±2000
V
V(ESD-CDM)
Charged Device Mode (CDM)
ANSI/ESDA/JEDEC JS-002-2014
Classification, Class: C0b
±200
V
ILATCH-UP
JEDEC STANDARD NO.78E APRIL 2016
Temperature Classification,
Class: I
±150
mA
Min
Max
Unit
–40
125
°C
Operating temperature range
-40
85
°C
Input voltage VIN
4.5
17
V
Output current
0
3
A
Recommended Operating Conditions
Item
Operating junction temperature
(1)
Note (1): All limits specified at room temperature (TA = 25°C) unless otherwise specified. All room temperature
limits are 100% production tested. All limits at temperature extremes are ensured through correlation using standard
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RY9135
17V 3A 600KHz ECOT Sync Step-Down Regulator
Statistical Quality Control (SQC) methods. All limits are used to calculate Average Outgoing Quality Level (AOQL).
Thermal Information
Item
Description
(1)(2)
Value
Unit
105
°C/W
RθJA
Junction-to-ambient thermal resistance
RθJC(top)
Junction-to-case (top) thermal resistance
55
°C/W
RθJB
Junction-to-board thermal resistance
17.5
°C/W
ψJT
Junction-to-top characterization parameter
3.5
°C/W
ψJB
Junction-to-board characterization parameter
17.5
°C/W
Note (1): The package thermal impedance is calculated in accordance to JESD 51-7.
Note (2): Thermal Resistances were simulated on a 4-layer, JEDEC board.
Electrical Characteristics (1) (2)
VIN=12V, TA=25°C, unless otherwise specified.
Parameter
Test Conditions
Input Voltage Range
Min
Typ.
4.5
Supply Current (Quiescent)
VEN =3.0V
Supply Current (Shutdown)
VEN =0 or EN = GND
Feedback Voltage
0.6
0.746
0.765
Max
Unit
17
V
0.8
mA
4
uA
0.784
V
High-Side Switch On-Resistance
ISW=100mA
70
mΩ
Low-Side Switch On-Resistance
ISW=-100mA
50
mΩ
Valley Switch Current Limit
4
A
Over Voltage Protection Threshold
18
V
Switching Frequency
600
KHz
94
%
89
nS
Maximum Duty Cycle
VFB=90%
Minimum Off-Time
EN Rising Threshold
1.4
V
EN Falling Threshold
Wake up VIN Voltage
Under-Voltage Lockout Threshold
Shutdown VIN Voltage
4.3
V
4.5
V
3.8
V
500
mV
Soft Start
1.5
mS
Thermal Shutdown
160
℃
Thermal Hysteresis
30
℃
Hysteresis VIN voltage
3.6
0.8
Note (1): MOSFET on-resistance specifications are guaranteed by correlation to wafer level measurements.
Note (2): Thermal shutdown specifications are guaranteed by correlation to the design and characteristics analysis.
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RY9135
17V 3A 600KHz ECOT Sync Step-Down Regulator
Typical Performance Characteristics (1) (2)
Note (1): Performance waveforms are tested on the evaluation board.
Note (2): VIN =12V, VOUT=3.3V, TA = +25ºC, unless otherwise noted.
Efficiency vs Load Current
Load Regulation
Line Regulation
VOUT=5V, 3.3V, 1.2V
VOUT=5V, 3.3V, 1.2V
VOUT=3.3V
Output Ripple Voltage
Output Ripple Voltage
Output Ripple Voltage
VIN=12V, VOUT=3.3V, IOUT=0A
VIN=12V, VOUT=3.3V, IOUT=1.5A
VIN=12V, VOUT=3.3V, IOUT=3A
Loop Response
Output Short
Short Circuit Entry
VIN=12V, VOUT=3.3V, IOUT=1.5A-3A
VIN=12V, VOUT=3.3V
VIN=12V, VOUT=3.3V
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RY9135
17V 3A 600KHz ECOT Sync Step-Down Regulator
Short Circuit Recovery
Enable Startup at No Load
Enable Shutdown at No Load
VIN=12V, VOUT=3.3V
VIN=12V, VOUT=3.3V, IOUT=0A
VIN=12V, VOUT=3.3V, IOUT=0A
Enable Startup at Full Load
Enable Shutdown at Full Load
Power Up at No Load
VIN=12V, VOUT=3.3V, IOUT=3A
VIN=12V, VOUT=3.3V, IOUT=3A
VIN=12V, VOUT=3.3V, IOUT=0A
Power Up at Full Load
VIN=12V, VOUT=3.3V, IOUT=3A
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RY9135
17V 3A 600KHz ECOT Sync Step-Down Regulator
Functional Block Diagram
IN
Internal
Regulator
EN
VCC
BS
UVLO
On-Time
Bias&Voltage
Reference
HICCUP
Control
VSHORT
Reference
FB
PWM
Reference
SW
Driver
OC
OCL
Reference
Ripple Gen
SW
GND
Block Diagram
Functions Description
Internal Regulator
The RY9135 is a current mode step down DC/DC converter that provides excellent transient response with no extra
external compensation components. This device contains an internal, low resistance, high voltage power MOSFET,
and operates at a high 600KHz operating frequency to ensure a compact, high efficiency design with excellent AC
and DC performance.
Error Amplifier
The error amplifier compares the FB pin voltage with the internal FB reference (VFB) and outputs a current
proportional to the difference between the two. This output current is then used to charge or discharge the internal
compensation network, which is used to control the power MOSFET current. The optimized internal compensation
network minimizes the external component counts and simplifies the control loop design.
Under-Voltage Lockout (UVLO)
Under-voltage lockout (UVLO) protects the chip from operating at an insufficient supply voltage. UVLO protection
monitors the internal regulator voltage. When the voltage is lower than UVLO threshold voltage, the device is shut
off. When the voltage is higher than UVLO threshold voltage, the device is enabled again.
Thermal Shutdown
Thermal shutdown prevents the chip from operating at exceedingly high temperatures. When the silicon die
temperature exceeds 160°C, it shuts down the whole chip. When the temperature falls below its lower threshold
(Typ. 130°C) the chip is enabled again.
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RY9135
17V 3A 600KHz ECOT Sync Step-Down Regulator
Internal Soft-Start
The soft-start is implemented to prevent the converter output voltage from overshooting during startup. When the
chip starts, the internal circuitry generates a soft-start voltage (SS) ramping up from 0V to 0.765V. When it is lower
than the internal reference (REF), SS overrides REF so the error amplifier uses SS as the reference. When SS is
higher than REF, REF regains control. The SS time is internally max to 1.5ms.
Over Current Protection and Hiccup
The RY9135 has cycle-by-cycle over current limit when the inductor current peak value exceeds the set current
limit threshold. Meanwhile, output voltage starts to drop until FB is below the Under-Voltage (UV) threshold. Once
a UV is triggered, the RY9135 enters hiccup mode to periodically restart the part. This protection mode is especially
useful when the output is dead-short to ground. The average short circuit current is greatly reduced to alleviate the
thermal issue and to protect the regulator. The RY9135 exits the hiccup mode once the over current condition is
removed.
Startup and Shutdown
If both VIN and EN are higher than their appropriate thresholds, the chip starts. The reference block starts first,
generating stable reference voltage and currents, and then the internal regulator is enabled. The regulator provides
stable supply for the remaining circuitries. Three events can shut down the chip: EN low, VIN low and thermal
shutdown. In the shutdown procedure, the signaling path is first blocked to avoid any fault triggering. The comp
voltage and the internal supply rail are then pulled down. The floating driver is not subject to this shutdown
command.
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RY9135
17V 3A 600KHz ECOT Sync Step-Down Regulator
Applications Information
Setting the Output Voltage
RY9135 require an input capacitor, an output capacitor and an inductor. These components are critical to the
performance of the device. RY9135 are internally compensated and do not require external components to achieve
stable operation. The output voltage can be programmed by resistor divider.
𝑉𝑂𝑈𝑇 = 𝑉𝐹𝐵 ×
𝑅1 + 𝑅2
𝑅2
VOUT(V)
R1(KΩ)
R2(KΩ)
RT(KΩ)
L1(μH)
C1(nF)
CIN(μF)
COUT(μF)
CFF (pF) Opt.
1.0
3.07
10
Non or 0
1.5
100
22
22×2
CFF Chapter
1.05
3.73
10
Non or 0
1.5
100
22
22×2
CFF Chapter
1.2
5.69
10
Non or 0
1.5
100
22
22×2
CFF Chapter
1.5
9.61
10
Non or 0
2.2
100
22
22×2
CFF Chapter
1.8
13.53
10
Non or 0
2.2
100
22
22×2
CFF Chapter
2.5
22.68
10
Non or 0
2.2
100
22
22×2
CFF Chapter
3.3
33.14
10
Non or 0
2.2
100
22
22×2
CFF Chapter
5.0
55.36
10
Non or 0
2.2
100
22
22×2
CFF Chapter
All the external components are the suggested values, the final values are based on the application testing results.
Selecting the Inductor
The recommended inductor values are shown in the Application Diagram. It is important to guarantee the inductor
core does not saturate during any foreseeable operational situation. The inductor should be rated to handle the
maximum inductor peak current: Care should be taken when reviewing the different saturation current ratings that
are specified by different manufacturers. Saturation current ratings are typically specified at 25°C, so ratings at
maximum ambient temperature of the application should be requested from the manufacturer. The inductor value
can be calculated with:
𝐿=
𝑉𝑂𝑈𝑇 × (𝑉𝐼𝑁 − 𝑉𝑂𝑈𝑇 )
𝑉𝐼𝑁 × ∆𝐼𝐿 × 𝐹𝑂𝑆𝐶
Where ΔIL is the inductor ripple current. Choose inductor ripple current to be approximately 30% to 40% of the
maximum load current. The maximum inductor peak current can be estimated as:
𝐼𝐿(𝑀𝐴𝑋) = 𝐼𝐿𝑂𝐴𝐷 +
∆𝐼𝐿
2
Under light load conditions below 100mA, larger inductance is recommended for improved efficiency. Larger
inductances lead to smaller ripple currents and voltages, but they also have larger physical dimensions, lower
saturation currents and higher linear impedance. Therefore, the choice of inductance should be compromised
according to the specific application.
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RY9135
17V 3A 600KHz ECOT Sync Step-Down Regulator
Selecting the Input Capacitor
The input current to the step-down converter is discontinuous and therefore requires a capacitor to supply AC current
to the step-down converter while maintaining the DC input voltage. For a better performance, use ceramic capacitors
placed as close to VIN as possible and a 0.1µF input capacitor to filter out high frequency interference is
recommended. Capacitors with X5R and X7R ceramic dielectrics are recommended because they are stable with
temperature fluctuations.
The capacitors must also have a ripple current rating greater than the maximum input ripple current of the converter.
The input ripple current can be estimated with Equation:
𝑉𝑂𝑈𝑇
𝑉𝑂𝑈𝑇
𝐼𝐶𝐼𝑁 = 𝐼𝑂𝑈𝑇 × √
× (1 −
)
𝑉𝐼𝑁
𝑉𝐼𝑁
From the above equation, it can be concluded that the input ripple current reaches its maximum at VIN=2VOUT where
𝐼
I𝐶𝐼𝑁 = 𝑂𝑈𝑇
. For simplification, choose an input capacitor with an RMS current rating greater than half of the
2
maximum load current.
The input capacitance value determines the input voltage ripple of the converter. If there is an input voltage ripple
requirement in the system, choose the input capacitor that meets the specification. The input voltage ripple can be
estimate with Equation:
∆𝑉𝐼𝑁 =
𝐼𝑂𝑈𝑇
𝑉𝑂𝑈𝑇
𝑉𝑂𝑈𝑇
×
× (1 −
)
𝐹𝑂𝑆𝐶 × 𝐶𝐼𝑁
𝑉𝐼𝑁
𝑉𝐼𝑁
Similarly, when VIN=2VOUT, input voltage ripple reaches its maximum of ∆𝑉𝐼𝑁 =
1
4
𝐼𝑂𝑈𝑇
.
𝑂𝑆𝐶 ×𝐶𝐼𝑁
×𝐹
Selecting the Output Capacitor
An output capacitor is required to maintain the DC output voltage. The output voltage ripple can be estimated with
Equation:
∆𝑉𝑂𝑈𝑇 =
𝑉𝑂𝑈𝑇
𝑉𝑂𝑈𝑇
1
× (1 −
) × (𝑅𝐸𝑆𝑅 +
)
𝐹𝑂𝑆𝐶 × 𝐿
𝑉𝐼𝑁
8 × 𝐹𝑂𝑆𝐶 × 𝐶𝑂𝑈𝑇
There are some differences between different types of capacitors. 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 can be estimated with Equation:
∆𝑉𝑂𝑈𝑇 =
𝑉𝑂𝑈𝑇
2
8 × 𝐹𝑂𝑆𝐶 × 𝐿 × 𝐶𝑂𝑈𝑇
× (1 −
𝑉𝑂𝑈𝑇
)
𝑉𝐼𝑁
A larger output capacitor can achieve a better load transient response, but the maximum output capacitor limitation
should also be considered in the design application. If the output capacitor value is too high, the output voltage will
not be able to reach the design value during the soft-start time and will fail to regulate. The maximum output
capacitor value (COUT_MAX) can be limited approximately with Equation:
𝐶𝑂𝑈𝑇_𝑀𝐴𝑋 = (𝐼𝐿𝐼𝑀_𝐴𝑉𝐺 − 𝐼𝑂𝑈𝑇 ) × 𝑇𝑆𝑆 /𝑉𝑂𝑈𝑇
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RY9135
17V 3A 600KHz ECOT Sync Step-Down Regulator
Where LLIM_AVG is the average start-up current during the soft-start period, and TSS is the soft- start time.
On the other hand, special attention should be paid when selecting these components. The DC bias of these
capacitors can result in a capacitance value that falls below the minimum value given in the recommended capacitor
specifications table.
The ceramic capacitor’s actual capacitance can vary with temperature. The capacitor type X7R, which operates over
a temperature range of −55°C to +125°C, will only vary the capacitance to within ±15%. The capacitor type X5R
has a similar tolerance over a reduced temperature range of −55°C to +85°C. Many large value ceramic capacitors,
larger than 1uF are manufactured with Z5U or Y5V temperature characteristics. Their capacitance can drop by more
than 50% as the temperature varies from 25°C to 85°C. Therefore, X5R or X7R is recommended over Z5U and
Y5V in applications where the ambient temperature will change significantly above or below 25°C.
Feed-Forward Capacitor (CFF)
RY9135 has internal loop compensation, so adding CFF is optional. Specifically, for specific applications, if
necessary, consider whether to add feed-forward capacitors according to the situation.
The use of a feed-forward capacitor (CFF) in the feedback network is to improve the transient response or higher
phase margin. For optimizing the feed-forward capacitor, knowing the cross frequency is the first thing. The cross
frequency (or the converter bandwidth) can be determined by using a network analyzer. When getting the cross
frequency with no feed-forward capacitor identified, the value of feed-forward capacitor (CFF) can be calculated
with the following equation:
𝐶𝐹𝐹 =
1
1
1
1
×√ ×( + )
2𝜋 × 𝐹𝐶𝑅𝑂𝑆𝑆
𝑅1
𝑅1 𝑅2
Where FCROSS is the cross frequency.
To reduce transient ripple, the feed-forward capacitor value can be increased to push the cross frequency to higher
region. Although this can improve transient response, it also decreases phase margin and cause more ringing. In the
other hand, if more phase margin is desired, the feed-forward capacitor value can be decreased to push the cross
frequency to lower region.
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RY9135
17V 3A 600KHz ECOT Sync Step-Down Regulator
PC Board Layout Consideration
PCB layout is very important to achieve stable operation. It is highly recommended to duplicate EVB layout for
optimum performance. If change is necessary, please follow these guidelines for reference.
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. VOUT, 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.
Top Layer
Bottom Layer
Sample Board Layout
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RY9135
17V 3A 600KHz ECOT Sync Step-Down Regulator
Package Description
SOT23-6
2.80
3.00
0.95
BSC
0.60
TYP
1.20
TYP
EXAMPLE
TOP MARK
AAAAA
1.50
2.60
1.70
3.00
2.60
TYP
PIN 1
TOP VIEW
RECOMMENDED PAD LAYOUT
GAUGE PLANE
0.25 BSC
0.90
1.30
1.45 MAX
SEATING PLANE
0.30
0.50
0.95 BSC
FRONT VIEW
0.00
0.15
0°~8°
0.30
0.55
0.09
0.20
SIDE VIEW
NOTE:
1. CONTROL DIMENSION IS IN INCHES. DIMENSION IN BRACKET IS IN MILLIMETERS.
2. PACKAGE LENGTH DOES NOT INCLUDE MOLD FLASH, PROTRUSIONS OR GATE BURRS.
3. PACKAGE WIDTH DOES NOT INCLUDE INTERLEAD FLASH OR PROTRUSIONS.
4. LEAD COPLANARITY (BOTTOM OF LEADS AFTER FORMING) SHALL BE 0.004" INCHES MAX.
5. DRAWING CONFORMS TO JEDEC MS-012, VARIATION BA.
6. DRAWING IS NOT TO SCALE.
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