SP1236FH

Wide Input Range CC/CV Synchronous Buck Regulator

Unauthorized Photocopy and Duplication Prohibited

Features General Description

 8V ~ 40V Supply Voltage Range The SP1236FH is a synchronous buck Regulator with
 45V Input Voltage Surge output current to 3.1A. It is designed to allow for operating
 42V Input Over Voltage Protection a wide supply voltage range from 8V to 40V. The internal
 3% Voltage Reference Accuracy compensation requires a minimum number of readily
 7% Constant Current Accuracy available standard external components.
 Cycle by Cycle Current Limit
The SP1236FH operates in the CC(Constant output
 External Optional Current Limit Mode
Current) mode or CV(Constant output Voltage) mode, and
 Programmable Frequency（60KHz ~ 1MHz）
the OCP current value is set by current sensing power
 Built in Adjustable Line-Compensation
resisters or setting non power resisters.
 Hiccup Short Circuit Protection
 Duty Cycle Range (0~100%) The SP1236FH is suitable for the DC/DC switching power
 Internal Soft Start 3ms applications when requested the current limit function.
 CC/CV Mode Control The devices are available in SOP-8L package and require
 SOP-8L Package very few external devices for operation.

Applications
 Car Chargers
 Portable Charger Devices
 DC/DC Converters with Current Limit

Typical Application Circuit

Figure1. Typical Application of SP1236FH(High-accuracy Current Limit)

Note1：
1.RCS=66mV/Ilimit., RCS is Power Resistor.
2.RT=24000K/fosc, The default frequency is 120KHz when keeping RT pin float.

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 SP1236FH
Wide Input Range CC/CV Synchronous Buck Regulator

Figure2. Typical Application of SP1236FH(Low-cost Current Limit)

Note2：
1.R4>25KΩ.
2. Iout =3.1A recommend R4=100K.
3.RT=24000K/fosc, The default frequency is 120KHz when keeping RT pin float.

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 SP1236FH
Wide Input Range CC/CV Synchronous Buck Regulator

Pin Function Description

FB 1 8 GND
RT 2 7 GND
SEN 3 6 SW
VIN 4 5 SW

Figure 3. Pin Configuration

Pin No. Pin Name Function Description

Feedback Pin. The voltage at this pin is regulated to 1.2V. Connect to the resistor divider
1 FB
between output and GND to set the output voltage.

2 RT Frequency Setting Pin . The pin can float.

The Current Limit Pin. When connected to the Power resistor between output negative and
GND, and the SEN Pin is connected to output negative, the current limit is set by
3 SEN
66mV/Rsen. When the SEN Pin is connected Non Power resistor to GND, the current limit
is set by note2.
Power Supply Input. Bypass this pin with a 1uF ceramic capacitor to GND, placed as close
4 VIN
to the IC as possible.

5.6 SW Power Switching Output to External Inductor.

Ground. Connect this pin to a large PCB copper area for best heat dissipation, Return FB
7.8 GND
to this GND and connect this GND to power GND at a single point for best noise immunity.

Ordering and Marking Information

Part Number Package Description Top Marking Package Form

SP1236 SOP-8L SP1236FH SOP-8L

SPT SP1236FH Package Code

Product Type

Company Logo
XXXXXX
Internal information Code

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 SP1236FH
Wide Input Range CC/CV Synchronous Buck Regulator

Absolute Maximum Ratings

Characteristics Symbol Rating Units

Supply Input Voltage VIN -0.3 to +45 V
SW to GND -1 to +VIN+1 V
FB,RT, SEN to GND -0.3 to +7 V
ESD HBM(Human Body Mode) ±2K V
ESD MM(Machine Mode) ±200 V
Power Dissipation, PD @TA=25℃ PD (TJ-TA)/ θJA W
Thermal Resistance from Junction to case θJC 40 ℃/W
Thermal Resistance from Junction to ambient θJA 160 ℃/W
Note3：
1. Stresses listed as the above “Absolute Maximum Ratings” may cause permanent damage to the device.
These are for stress ratings. Functional operation of the device at these or any other conditions beyond those indicated in
the operational sections of the specifications is not implied. Exposure to absolute maximum rating conditions for extended
periods may remain possibility to affect device reliability.
2. Devices are ESD sensitive. Handling precaution recommended.
3. θ JA is measured in the natural convection at T A= 25°C on a high effective thermal conductivity test board of JEDEC51-7
thermal measurement standard.

Recommended Operating Conditions

Symbol Description Value Units

TST Storage Temperature Range -65 to +150 ℃

TJ Junction Temperature -40 to +150 ℃

TOP Operating Temperature -40 to +85 ℃

Lead Temperature Range(Soldering 10sec) 260 ℃

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 SP1236FH
Wide Input Range CC/CV Synchronous Buck Regulator

Block Diagram

OTP POR VIN

1.35V
OVP Current
sense
Fault
0.4V
Logics
CSP
FB

CC
COMP
CV EA Gate
Control SW
VREF

Current
SEN Sense
66mV
ramp

Oscillator Zero detect

GND
Current limit

RT

Figure 4. Block diagram of SP1236FH

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 SP1236FH
Wide Input Range CC/CV Synchronous Buck Regulator

Electrical Characteristics
VCC = 12V, TA = +25°C, unless otherwise specified
Characteristics Symbol Test Conditions Min Typ Max Units
Supply Voltage Range VIN Vcc 8 - 40 V
ICC Vin=12V,Vout=5V,no load - 0.6 - mA
Quiescent Current
ICC Vin=24V,Vout=5V,no load - 0.4 - mA
Power-On-Reset
VCCRTH Vcc Rising. - 7.5 -
VCC POR Threshold V
VCCFTH Vcc Falling. - 6.0 -
VIN_OVP VIN Rising. - 42 -
Input OVP Threshold V
VIN_OVP_HYS VIN Falling. - 2.0 -
Oscillator
Normal PWM Frequency FOSC IOUT=200 mA，RT float 90 120 150 KHz
Duty Cycle Range Duty 0 - 100 %
Reference
Reference Voltage VREF - 1.2 - V
Reference Voltage Tolerance -3 - +3 %
Line compensation Current IFB Iout=1A - 0.44 - uA
Current Sense Amplifier (Power Resistors)
SEN Voltage VSEN - 66 - mV
SEN Voltage Tolerance -7 - +7 %
Current Set (Non Power Resistors)
Rsen=68K Ilimit Vin=12V,Vout=5V 3.5 A
Rsen=51K Ilimit Vin=12V,Vout=5V 2.8 A
Protection
Over Temperature Shutdown - 160 - ℃
Over Temperature Hysteresis - 40 - ℃
Soft Start
Soft Start Time TSS - 3 - ms
Recycle Time - 500 - ms
Output Short Circuit Protect Section
Short Circuit Fold Back Voltage VSCP - 0.4 - V
MOSFET
Up PMOS On Resestance Rdson 40 mΩ
Down NMOS On Resestance Rdson 26 mΩ

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 SP1236FH
Wide Input Range CC/CV Synchronous Buck Regulator

Functional Description
Rsen 100K

CV/CC mode control Iout 3.1A

The SP1236FH provides CC/CV function. The Constant
output Current control Mode and Constant output Voltage Oscillator Frequency
control Mode. The SP1236FH oscillator frequency is set by a single
external resistor connected between the RT pin and the
Over Current Protection
GND pin. The resistor should be located very close to the
The SP1236FH provides over current protection. A drop
device and connected directly to the pins of the IC (RT
voltage on the current sensing resister is over the OCP
and GND). The oscillator frequency rises when the
value, the OCP function will shut down the controller.
resistor RT falls. To determine the timing resistance for a
Soft Start given switching frequency, use the equation below:
The SP1236FH has internal soft start function to control 24000K
f(KHz)=
rise rate of the output voltage and limits the large inrush RT
current at start up. The typical soft start interval is about Output Short-Circuit Protection
3mS. The SP1236FH provides output short-circuit protection
function. When VOUT is short (VFB<0.4V), the auto restart
Power on Reset
function can be started that restart the regulator cycle by
A power-on reset circuit monitors the input voltage. When
cycle. The cycle time is set by internal counter.
the input voltage exceeds 7.5V, the converter will start
operation. Once input voltage falls below 6.0V, the
controller will shut down.

Over Temperature Protection

The SP1236FH provides over temperature protection.
The OTP will shut down the converter when junction
temperature exceeds 160℃.Once the junction
temperature cools down by approximately 40℃, the
converter will resume normal operation. 35mS 500mS

Current Limit Protection

Figure 5. short-circuit protection time
The SP1236FH provides two kinds of current limit Mode.
When connected to the Power resistor between output
negative and GND, and the SEN Pin is connected to
output negative, the current limit set according to the
following equation:

66mV
CurrentLimit(A)=
RSEN
When the SEN Pin is connected the Non Power Resistor
to GND, the current limit set according to the following:

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 SP1236FH
Wide Input Range CC/CV Synchronous Buck Regulator
Higher inductance reduces the peak-to-peak ripple
APPLICATION INFORMATION current. The tradeoff for high inductance value is the
increase in inductor core size and series resistance, and
Output Voltage Setting
the reduction in current handling capability. In general,
VOUT
select an inductance value L based on ripple current
SP1236FH RFB1
requirement:
VOUT  VIN  VOUT 
FB L
VIN fSW IOUTMAX K RIPPLE
RFB2
Where VIN is the input voltage, VOUT is the output voltage,
fSW is the switching frequency, IOUTMAX is the maximum
Figure 6. Output Voltage Setting
output current, and KRIPPLE is the ripple factor. Typically,
Figure 6 shows the connections for setting the output
choose KRIPPLE=30% to correspond to the peak-to-peak
voltage. Select the proper ratio of the two feedback
ripple current being 30% of the maximum output current.
resistors RFB1 and RFB2 based on the output voltage.
Typically, use RFB2>10kΩ and determine RFB1 from the With this inductor value, the peak inductor current is IOUT ×
following equation: (1+KRIPPLE/2). Make sure that this peak inductor current is
 VOUT  less than the controller’s current limit. Finally, select the
RFB1  RFB 2   1
 1.2  inductor core size so that it does not saturate at the peak
inductor current.
Output Cable Resistance Compensation
Input Capacitor
To compensate for resistive voltage drop across the
The input capacitor needs to be carefully selected to
charger's output cable, the SP1236FH integrates a simple,
maintain sufficiently low ripple at the supply input of the
user-programmable cable voltage drop compensation
converter. A low ESR capacitor is highly recommended.
using the impedance at the FB pin. RFB1 is the high side
Since large current flows in and out of this capacitor
resistor of voltage divider.
during switching, its ESR also affects efficiency.
 R 
VOUT  (1  FB1 )  1.2  RFB1  IOUT  0.44 The input capacitance needs to be higher than 100μF. The
 RFB 2 
best choice is the ceramic type, however, low ESR
tantalum or electrolytic types may also be used provided
that the RMS ripple current rating is higher than 50% of
the output current. The input capacitor should be placed
close to the VIN and GND pins of the IC, with the shortest
traces possible. In the case of tantalum or electrolytic
types, they can be further away if a small parallel 1μF
ceramic capacitor is placed right next to the IC. Especially
C2 capacitor should be placed as close as possible to the
VIN pin.

Output Capacitor
Figure 7. 12V in to 5V out Cable Compensation
The output capacitor also needs to have low ESR to keep
Inductor Selection low output voltage ripple. The output ripple voltage is:
The inductor maintains a continuous current to the output VIN
VRIPPLE  IOUT KRIPPLE RESR 
load. This inductor current has a ripple that is dependent 28  fSW
2
LCOUT
on the inductance value: Where IOUTMAX is the maximum output current, KRIPPLE is

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 SP1236FH
Wide Input Range CC/CV Synchronous Buck Regulator
the ripple factor, RESR is the ESR of the output capacitor,
fSW is the switching frequency, L is the inductor value, and
COUT is the output capacitance. In the case of ceramic
output capacitors, RESR is very small and does not
contribute to the ripple. Therefore, a lower capacitance
value can be used for ceramic type. In the case of
tantalum or electrolytic capacitors, the ripple is dominated
by RESR multiplied by the ripple current. In that case, the
output capacitor is chosen to have sufficiently low ESR.

For ceramic output capacitor, typically choose a

capacitance of about 470μF. For tantalum or electrolytic
capacitors, choose a capacitor with less than 50mΩ ESR.

PCB Layout Recommendations

1. PCB trance defined as SW node, which connects to the
inductor, should be as short and wide as possible.
2. Inductance between the SW terminal and the output
VOUT as far as possible with the ground wire to reduce
the output side of the switch coupling.
3. ALL sensitive analog traces such as SEN and FB
should place away from high-voltage switching nodes SW
nodes to avoid coupling.
4. Input bypass capacitor should be placed to the IN pin
as close as possible.
5. Feedback resistor should be placed to the FB pin as
close as possible.
6. Gather the ground terminals of the VIN capacitor(s),
VOUT capacitor(s), and the source of the low-side
MOSFETs as close as possible. Signal ground and power
ground should be connected strongly together near the
device.
7.The ground of input capacitance and output capacitance
should be placed as close as possible.

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 SP1236FH
Wide Input Range CC/CV Synchronous Buck Regulator

Package Information（Units:mm）

D
A3 h 0.2
A2 A 5
c L
θ
A1 L1

E1 E

b e

Dimensions in Millimeters
Symbol
Min. Nom. Max.
A - - 1.75
A1 0.05 - 0.15
A2 1.30 1.40 1.50
A3 0.60 0.65 0.70
D 4.70 4.90 5.10
E 5.80 6.00 6.20
E1 3.70 3.90 4.10
b 0.39 - 0.48
c 0.21 - 0.26
e 1.27BSC
h 0.25 - 0.50
L 0.50 - 0.80
L1 1.05BSC
θ 0 - 8°

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 SP1236FH
Wide Input Range CC/CV Synchronous Buck Regulator

Restrictions on Product Use

 Si-Power is continually working to improve the quality and reliability of its products. Nevertheless, semiconductor
devices in general can malfunction or fail due to their inherent electrical sensitivity and vulnerability to physical
stress. It is the responsibility of the buyer, when utilizing Si-Power products, to comply with the standards of safety
in making a safe design for the entire system, and to avoid situations in which a malfunction or failure of such
Si-Power products could cause loss of human life, bodily injury or damage to property.

 In developing your designs, please ensure that Si-Power products are used within specified operating ranges as
set forth in the most recent Si-Power products specifications.

 The information contained herein is subject to change without notice.

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