SCT12A1
SILICON CONTENT
TECHNOLOGY
2.7V-14V Vin, 30W Fully Integrated Synchronous Boost Converter
with Load Disconnection Control
FEATURES
Wide Input Voltage Range: 2.7V-14.0V
Wide Output Voltage Range: 4.5V-14.6V
Fully Integrated 13mΩ High Side FET and
11mΩ Low Side FET
Up to 92% Efficiency at Vin=3.6V, Vout=9V, and
Iout=3A
Up to 12A Switch Current and Programmable
Peak Current Limit
Load Disconnection Control with an External PChannel MOSFET
Typical Shut-down Current: 1uA
Programmable Switching Frequency: 200kHz2.2MHz
Selectable PFM or Forced PWM Mode
Programmable Soft Start
Output and Feedback Overvoltage Protection
Thermal Shutdown Protection: 150°C
Available in DFN-20 3.5mmx4.5mm Package
APPLICATIONS
DESCRIPTION
Bluetooth Audio
Power Banks
POS System
E-Cigarette
USB Power Delivery
The SCT12A1 is a high efficiency synchronous boost
converter with fully integrated a 13mΩ high-side
MOSFET and an 11mΩ low-side MOSFET,
supporting 2.7V to 14V input voltage range and up to
12-A switch current. The switch current limit can be
adjustable with an external resistor.
The SCT12A1 adapts constant off-time peak current
control to provide fast transient. An external
compensation network allows flexibility setting loop
dynamics to achieve optimal transient performance at
different load conditions. Using MODE pin selects
either Pulse Frequency Modulation (PFM) operation
or forced Pulse Width Modulation (PWM) operation.
The SCT12A1 offers the gate control for an external
P-channel MOSFET to disconnect load from boost
converter output. This safety feature prevents the
damage on load from input shooting through to output
in shutdown or output hard short to ground condition.
The SCT12A1 monitors both output voltage and
feedback voltage to protect overvoltage condition. It
features cycle-by-cycle peak current limit and thermal
shutdown protection when the device over loads.
The device is available in a low-profile package DFN20L 3.5mmx4.5mmx0.9mm with enhanced thermal
power pad.
TYPICAL APPLICATION
Efficiency, Vout=9V
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1
SCT12A1
REVISION HISTORY
NOTE: Page numbers for previous revisions may differ from page numbers in the current version.
DEVICE ORDER INFORMATION
PART NUMBER
PACKAGE MARKING
PACKAGE DISCRIPTION
SCT12A1
12A1
20-Lead 3.5mm×4.5mm Plastic DFN
ABSOLUTE MAXIMUM RATINGS
MIN
BOOT
-0.3
MAX
UNIT
23.5
V
AGND
DESCRIPTION
Top View: 20-Lead Plastic DFN 3.5mmx4.5mm
VCC
Over operating free-air temperature unless otherwise
PIN CONFIGURATION
noted(1)
ILIM
EN
VIN, SW, VOUT, FSW,
FSW
PGATE
-0.3
18
COMP
SW
V
FB
VOUT
SW
-0.3
VCC, LIM，FB， EN,SS,
COMP, MODE, ENPGATEZ
Operating junction temperature
125
V
PGND
C
SW
VOUT
SW
VOUT
BOOT
MODE
VIN
ENPGATEZ
Storage temperature TSTG
(1)
(2)
-65
150
C
PGATE
(2)
SS
TJ
-40
5.5
Stresses beyond those listed under Absolute Maximum Rating may cause device permanent damage. The device is not guaranteed to
function outside of its Recommended Operation Conditions.
The IC includes over temperature protection to protect the device during overload conditions. Junction temperature will exceed 150°C
when over temperature protection is active. Continuous operation above the specified maximum operating junction temperature will
reduce lifetime
PIN FUNCTIONS
NAME
VCC
1
EN
2
FSW
3
SW
2
NO.
4,5,6,7
BOOT
8
VIN
9
SS
10
PGATE
11
PIN FUNCTION
Internal linear regulator output. Connect a 1uF or larger ceramic capacitor to
ground. VCC cannot to be externally driven. No additional components or loading
is recommended on this pin.
Enable logic input. A 800KΩ resistor connects this pin to ground inside. Floating
disables the device.
Place a resistor from this pin to SW to set the switching frequency.
Switching node of the boost converter.
Power supply for the high-side FET gate driver. Must connect a 0.1uF or greater
ceramic capacitor between BOOT pin and SW node.
Power supply input. Must be locally bypassed with a capacitor as close as possible
to the pin.
Place a ceramic cap from this pin to ground to program soft-start time. An internal
5uA current source pulls SS pin to VCC.
Gate driver output for an external P-channel MOSFET to disconnect load.
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SCT12A1
ENPGATEZ
12
MODE
13
VOUT
14,15,16
Connect the pin to ground to enable the load disconnection control. Directly short
to thermal pad under IC to reduce the C6 ground loop if grounding. 400KΩ internal
resistor connects this pin to VCC. Floating disables the load disconnection
protection.
Operation mode selection. 270KΩ internal resistor connects this pin to VCC.
Floating or Logic high enables PFM mode. Logic low enables forced PWM mode.
Boost converter output. Connect a 1uF decoupling capacitor as close to VOUT pins
and power ground pad as possible to reduce the ringing voltage of SW.
Feedback Input. Connect a resistor divider from VOUT to FB to set up output
voltage. The device regulates FB to the internal reference value of 1.2V typical.
Output of the error amplifier and switching converter loop compensation point.
Inductor peak current limit set point input. A resistor connecting this pin to ground
sets current limit through low-side power FET.
FB
17
COMP
18
ILIM
19
AGND
20
Analog ground. Analog ground should be used as the common ground for all small
signal analog inputs and compensation components. No electrical connection to
PGND inside.
PGND
21
Power ground. Must be soldered directly to ground planes using multiple vias
directly under the IC for improved thermal performance and electrical contact.
RECOMMENDED OPERATING CONDITIONS
Over operating free-air temperature range unless otherwise noted
PARAMETER
VIN
VOUT
TJ
DEFINITION
Input voltage range
Output voltage range
Operating junction temperature
MIN
MAX
UNIT
2.7
4.5
-40
14
14.6
125
V
V
°C
MIN
MAX
UNIT
-2
+2
kV
-0.5
+0.5
kV
ESD RATINGS
PARAMETER
VESD
DEFINITION
Human Body Model (HBM), per ANSI-JEDEC-JS-0012014 specification, all pins (1)
Charged Device Model (CDM), per ANSI-JEDEC-JS-0022014specification, all pins (2)
(1) HBM and CDM stressing are done in accordance with the ANSI/ESDA/JEDEC JS-001-2014 specification
THERMAL INFORMATION
PARAMETER
RθJA
RθJC
THERMAL METRIC
Junction to ambient thermal resistance (1)
Junction to case thermal resistance
(1)
DFN-20L
38
39
UNIT
°C/W
(1) SCT provides RθJA and RθJC numbers only as reference to estimate junction temperatures of the devices. RθJA and RθJC are not a
characteristic of package itself, but of many other system level characteristics such as the design and layout of the printed circuit
board (PCB) on which the SCT12A1 is mounted, thermal pad size, and external environmental factors. The PCB board is a heat sink
that is soldered to the leads and thermal pad of the SCT12A1. Changing the design or configuration of the PCB board changes the
efficiency of the heat sink and therefore the actual RθJA and RθJC.
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SCT12A1
ELECTRICAL CHARACTERISTICS
VIN=3.6V, TJ=-40°C~125°C, typical values are tested under 25°C.
SYMBO
L
PARAMETER
TEST CONDITION
MIN
Power Supply and Output
VIN
Operating input voltage
VOUT
Output voltage range
VIN_UVLO
Input UVLO
Hysteresis
ISD
Shutdown current
IQ
VCC
Quiescent current from VIN
Quiescent current from VOUT
Internal linear regulator
TYP
2.7
4.5V
VIN rising
EN=0, no load and measured
on VIN pin
EN=2V, no load, no switching
ENPGATEZ=floating
IVCC=5mA, VIN=6V
MAX
UNIT
14
V
14.6
V
2.6
200
2.7
V
mV
1
3
uA
1
120
4.8
150
uA
uA
V
1.220
1.228
100
V
V
nA
Reference and Control Loop
1.170
1.192
1.202
1.210
Reference voltage of FB
IFB
FB pin leakage current
GEA
VCOMP=1.5V
190
uS
VFB=VREF-200mV, VCOMP=1.5V
20
uA
ICOMP_SNK
Error amplifier trans-conductance
Error amplifier maximum source
current
Error amplifier maximum sink current
VFB=VREF+200mV, VCOMP=1.5V
20
uA
VCOMP_H
COMP high clamp
VFB=1V， RILIM=100KΩ
1.5
V
VCOMP_L
COMP low clamp
VFB=1.5V, RILIM=100KΩ,PFM
0.6
V
Power MOSFETs
RDSON_H
High side FET on-resistance
13
mΩ
RDSON_L
11
mΩ
ICOMP_SRC
Low side FET on-resistance
Current Limit
ILIM
Peak current limit
Enable and Mode
Enable high threshold
VEN
Enable low threshold
REN
Enable pull down resistance
RMODE
MODE high threshold
MODE low threshold
MODE pull-up resistance
ISS
Soft-start charging current
VMODE
RILIM=100kΩ
10.5
12
13
A
1.2
V
V
kΩ
4
270
V
V
kΩ
5
uA
kHz
VCC=5V
0.4
800
VCC=5V
1.5
Switching Frequency
FSW
Switching frequency
RFSW=301k, VOUT=12V
500
tON_MIN
Minimum on-time
RFSW=301k, VOUT=12V
150
200
ns
tOFF_MIN
Minimum off-time
RFSW=301k, VFB=0V
100
150
ns
4
V
Load Disconnection Control
VENPGATEZ_
ENPGATEZ voltage high threshold
H
VENPGATEZ_
L
RENPGATEZ
4
FPWM mode
PSM mode
VFB=1.2V
VREF
ENPGATEZ voltage low threshold
VCC=5V
VCC=5V
ENPGATEZ internal pull up
resistance
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1.5
V
400
All Rights Reserved
kΩ
SCT12A1
SYMBO
L
IPGATE
VPGATE_C
PARAMETER
TEST CONDITION
PGATE pull down current
Clamp voltage between PGATE and
VOUT
MIN
TYP
MAX
60
7.1
UNIT
uA
8
V
Protection
VOVP_VOUT
VOVP_VFB
TSD
Output overvoltage threshold
Hysteresis
Feedback overvoltage with respect
to reference voltage
Thermal shutdown threshold
Hysteresis
VOUT rising
VFB rising
VFB falling
TJ rising
15.4
250
110
105
150
20
V
mV
%
%
°C
°C
TYPICAL CHARACTERISTICS
Figure 1. Efficiency, Vout=9V, fsw=560KHz, PFM
Figure 3. Efficiency, Vout=12V, fsw=560KHz, 1-cell Battery
Figure 2. Efficiency, Vout=9V, fsw=560KHz, PWM
Figure 4. Efficiency, Vout=12V, fsw=560KHz, 2-cells Battery
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SCT12A1
16
Switch Peak Current Limit
14
12
10
8
6
4
2
0
50
100
150
200
250
300
350
Resistance (K Ohm)
Figure 5. Switching Frequency vs FSW Resistance
Figure 6. Inductor Peak Current Limit vs RLIM Resistance
600
160
Quiescent Current (uA)
140
Frequency (KHz)
590
580
570
560
120
100
80
60
40
20
550
0
-40
-20
0
20
40
60
Temperature
80
(OC)
100
120
140
-40
0
40
60
80
100
120
140
Figure 8. Quiescent Current vs Temperature
1.222
1.5
1.22
1.3
1.218
1.2
1.216
Reference Voltage (V)
1.4
1.1
1
0.9
0.8
0.7
0.6
0.5
0.4
0.3
0.2
1.214
1.212
1.21
1.208
1.206
1.204
1.202
1.2
1.198
PFM
PWM
1.196
0.1
0
1.194
-40
-20
0
20
40
60
80
100
120
140
-60
-40
-20
Temperature (OC)
Figure 9. Shutdown Current vs Temperature
6
20
Temperature (OC)
Figure 7. Frequency vs Temperature
Shutdown Current (uA)
-20
0
20
40
60
80
100
120
140
160
Temperature (OC)
Figure 10. Feedback Reference Voltage vs Temperature
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SCT12A1
Figure 11. Load Regulation (Vin=3.6V, Vout=9V)
Figure 12. Line Regulation
FUNCTIONAL BLOCK DIAGRAM
UVLO
VIN
9
VCC
BOOT
SW
SW
SW
SW
1
8
4
5
6
7
OTP
UVLO
Q2
BOOT
Regulator
LDO
Thermal
Sensor
FB
VOUT
Q1
HSD OC
Detect
11
Load
Disconnect
Control
Q
Q
S
R
PGATE
Selection
Mode
Selection
GM
ON/OFF and
Protection
VIN
34pF
ENPGATEZ
17
FB
10
SS
18
COMP
1.2V
UVLO OVP OTP
V/I
1/N
3
12
LDP
+
FSW
VOUT
5uA
+
13
16
400k
+
+
MODE
VOUT
VCC
ENP
270k
15
OVP
Dead Time and
PWM Control
Logic
LDP ENP
VCC
VOUT
OVP
+
+
PGATE
14
800k
1.2V
2
21
19
20
EN
PGND
ILIM
AGND
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SCT12A1
OPERATION
Overview
The SCT12A1 device is a fully integrated synchronous boost converter, which regulates output voltage higher than
input voltage. The constant off-time peak current mode control provides fast transient with pseudo fixed switching
frequency. When low-side MOSFET Q1 turns on, input voltage forces the inductor current rise. Sensed voltage on
low-side MOSFET peak current rises above the voltage of COMP. After the inductor current reaches the peak
current, the device turns off low-side MOSFET and inductor goes through body diode of high-side MOSFET Q2
during dead time. After dead time duration, the device turns on high-side MOSFET Q2 and the inductor current
decreases. Based on Vin and Vout voltage, the device predicts required off-time and turns off high-side MOSFET
Q2. This repeats on cycle-by-cycle based.
The voltage feedback loop regulates the FB voltage to a 1.2V reference with an internal trans-conductance error
amplifier. The feedback loop stability and transient response are optimized through an external loop compensation
network connected to the COMP pin.
The mode selection offers flexibility of design between forced Pulse Width Modulation (PWM) and Pulse Frequency
Modulation (PFM) operations. When MODE pin is connected to VCC or floats, the SCT12A1 works at PFM mode
to further increase the efficiency in light load condition. If MODE pin is connected to ground, the device works in
forced PWM mode with low output voltage ripple.
The quiescent current of SCT12A1 is 120uA typical under no-load condition and not switching. Disabling the device,
the typical supply shutdown current is 1μA.
A resistor connected between SW pin and the FSW pin sets the switching frequency. The wide switching frequency
range of 200 kHz to 2.2 MHz offers optimization on efficiency or size of filter components.
The SCT12A1 provides PGATE pin to control the gate of an external load disconnection P-channel MOSFET, which
completely disconnects the load from the input during output hard short or shutdown condition. During start-up, the
SCT12A1 gradually turns on the load disconnection switch to limit the inrush current. The protection circuitry quickly
turns off the disconnection switch when any severe over-current condition happens. Hiccup mode minimizes power
dissipation during prolonged output over current or short condition. The hiccup time is determined by external
programmable soft-start time.
The SCT12A1 device features adjustable soft-start time, cycle-by-cycle low-side FET current limit, over-voltage
protection, and over-temperature protection.
The SCT12A1 uses two separate ground pins to avoid ground bouncing due to the high switching current through
the N-channel power MOSFET. AGND pin sets the reference for all control functions. The source of the power
MOSFET connects to PGND pin. Both grounds must be connected to the thermal pad on the PCB at the closest
point.
VIN Power
The SCT12A1 is designed to operate from an input voltage supply range between 2.7 V to 14V. If the input supply
is located more than a few inches from the converter, additional bulk capacitance may be required in addition to the
ceramic bypass capacitors. A typical choice is ceramic capacitor with a value of 47μF or 2 x 22uF.
VCC Power
The internal VCC LDO provides the bias power supply for internal circuitries. A ceramic capacitor of no less than
1uF is required to bypass from VCC pin to ground. During starting up, input of VCC LDO is from VIN pin. Once the
output voltage at VOUT pin exceeds VIN voltage, VCC LDO switches its input to VOUT pin. This allows higher
voltage headroom of VCC at lower input voltage. The maximum current capability of VCC LDO is 130mA typical.
No additional components or loading are recommended on this pin.
8
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SCT12A1
Under Voltage Lockout UVLO
The SCT12A1 features UVLO protection for voltage rails of VIN, VCC and BOOT-SW from the converter
malfunctioning and the battery over discharging. The default VIN rising threshold is 2.6V typical at startup and falling
threshold is 2.4V typical at shutdown. The internal VCC LDO dropout voltage is about 100mV and the device is
disabled when VCC falling trips 2.1V typical threshold. The internal charge pump from BOOT to SW powers the
gate driver to high-side MOSFET Q2. The BOOT UVLO circuit monitors the capacitor voltage between BOOT pin
and SW pin. When the voltage of BOOT to SW falls below a preset threshold 3V typical, high-side MOSFET Q2
turns off. As a result, the device works as a non-synchronous boost converter.
Enable and Start-up
When applying a voltage higher than the EN high threshold (maximum 1.2V), the SCT12A1 enables all functions
and starts converter operation. To disable converter operation, EN voltage needs fall below its lower threshold
(minimum 0.4V). An internal 800KΩ resistor connects EN pin to the ground. Floating EN pin automatically disables
the device.
The SCT12A1 features programmable soft start to prevent inrush current during power-up. SS pin sources an
internal 5μA current charging an external soft-start capacitor CSS when EN pin exceeds turn-on threshold. The
device uses the lower voltage between the internal voltage reference 1.2V and the SS pin voltage as the reference
input voltage of error amplifier and regulates the output. The soft-start completes when SS pin voltage exceeds the
internal 1.2V reference. Use equation 1 to calculate the soft-start time (10% to 90%). When EN pin is pulled low to
disable the device, the SS pin will be discharged to ground.
t SS =
where
CSS ∗ VREF
ISS
(1)
tSS is the soft start time
VREF is the internal reference voltage of 1.2V
CSS is the capacitance connecting to SS pin
ISS is the source current of 5uA to SS pin
Adjustable Switching Frequency
The SCT12A1 features adjustable switching frequency from 200kHz to 2.2MHz. To set the switching frequency, an
external resistor between SW pin and FSW pin is a must to guarantee the proper operation. Use Equation 2 or the
curves in Figure 5 to determine the resistance for a given switching frequency. To reduce the solution size, one can
typically set the switching frequency as higher as possible, but need to consider the tradeoff of the thermal
dissipation and minimum on time of low-side power MOSFET.
6∗(
𝑅𝐹𝑅𝐸𝑄 =
where:
1
𝑓𝑆𝑊
− 𝑇𝐷𝐸𝐿𝐴𝑌 ∗
𝑉𝑂𝑈𝑇
𝑉𝐼𝑁
)
𝐶𝐹𝑅𝐸𝑄
(2)
fSW is the desired switching frequency
TDELAY = 90 ns
CFREQ = 34 pF
VIN is the input voltage
VOUT is the output voltage
Adjustable Peak Current Limit
The SCT12A1 boost converter implements cycle-by-cycle peak current limit function with sensing the internal lowFor more information www.silicontent.com © 2016 Silicon Content Technology Co., Ltd. All Rights Reserved
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SCT12A1
side power MOSFET Q1 during over current condition. While the Q1 is turned on, its conduction current is monitored
by the internal sensing circuitry. Once the low-side MOSFET Q1 current exceeds the limit, it turns off immediately.
An external resistor connecting ILIM pin to ground sets the low-side MOSFET Q1 peak current limit threshold. Use
Equation 3 or Figure 6 to calculate the peak current limit.
𝐼𝐿𝐼𝑀 =
1200
𝑅𝐿𝐼𝑀
(3)
where:
ILIM is the peak current limit
RLIM is the resistance between ILIM pin to ground.
This current limit function is realized by detecting the current flowing through the low-side MOSFET. The current
limit feature loses function in the output hard short circuit conditions. At normal operation, when the output hard
shorts to ground, there is a direct path to short the input voltage through high-side MOSFET Q2 or its body diode
even the Q2 is turned off. This could damage the circuit components and cause catastrophic failure at load circuit.
Load Disconnection Control (SCT Patent Filed)
For both non-synchronous and synchronous boost converter, there is a non-fully controlled current path from
converter input to output load through the diode or the high-side MOSFET body diode. During start up, once VIN is
present, VOUT is moved to VIN level due to the direct path from input to output even when the device is shut down
or the load is not ready. The presence of unwanted output voltage before system start up sequence could cause
system to latch off or malfunction. When the output shorts to ground at fault condition, the direct path causes the
inductor current running away, the converter active components damages, and the catastrophic failure at load circuit.
To address the above issues, the SCT12A1 provides a solution to insert an external P-channel MOSFET to
disconnect the load from the converter output in application as shown in Figure 13. Choosing a lower Rdson of the
disconnection P-channel MOSFET Q3 reduces impact on the efficiency. The source of Q3 needs connect to VOUT
pin. Output capacitor is required at both VOUT pin and the source of P-channel MOSFET to maintain the loop
stability.
In Figure 13, connecting ENPGATEZ pin to ground enables load disconnection features of SCT12A1. PGATE pin
connecting to gate of Q3 has a constant sink current pulling down capability and a resistance pulling up capability.
During SCT12A1 starting up, internal circuitry softly starts up of P-channel MOSFET. When gate-source voltage of
external P-channel MOSFET is lower than the threshold voltage, the Q3 is turned on and the load is connected to
VOUT pin. The source-gate voltage of external P-channel MOSFET is clamped up to 8V when the P-channel
MOSFET is fully turned on.
To detect if SCT12A1 has serve over loading or output hard short condition, the SCT12A1 has the current sensing
scheme on internal high-side MOSFET during its turn-on state as shown Figure 13. When the high side MOSFET
over current is detected, SS pin is discharged to ground and the external P-channel MOSFET is turned off
immediately. The load is disconnected from the converter output. When high-side MOSFET is turned off, the
SCT12A1 compares the VIN and VOUT, if VOUT is lower than VIN 1V, the SCT12A1 shuts off the external Pchannel MOSFET and disconnect the load immediately as well.
If serve over current happens or output shorts to ground, the SCT12A1 minimizes the power dissipation by
implementing hiccup mode as shown in Figure 14. For example, when internal high-side MOSFET over current
triggers load disconnection protection, SS pin resets and the boost converter stops switching. After SS pin starts
charging and reaches 1.2V, boost converter resumes to normal switching and starts to turn on P-channel MOSFET
again. The hiccup time can be calculated with external capacitance on SS pin as shown in equation 1. If the fault
condition disappears, the SCT12A1 resumes to normal operation automatically.
In extreme application case, starting up SCT12A1 with huge output capacitor C5B and heavy load might cause over
current protection. Increasing C5A capacitance accordingly enables startup normally.
10
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SCT12A1
L1
VIN
C7
SW
Q2
VOUT
Q1
Q3
VOUT_LOAD
C5A
C5B
HSD OC
Detect
8V
HSD_OC
PGATE
ENPGATEZ
EN_HSD
S
A
VOUT
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