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Single-chip Type with Built-in FET Switching Regulator Series
Simple Step-down Switching Regulator with Built-in Power MOSFET
BD9870FPS
No.09027EAT26
Description The BD9870FPS single-channel step-down switching regulator incorporates a Pch MOSFET capable of PWM operation at 900kHz, enabling use of a smaller coil, as well as circuitry that eliminates the need for external compensation - only a diode, coil, and ceramic capacitor are required - reducing board size significantly. Features 1) Maximum switching current: 1.5A 2) 2. Built-in Pch FET ensures high efficiency 3) Output voltage adjustable via external resistors 4) High switching frequency: 900kHz (fixed) 5) Soft start time: 5ms (fixed) 6) Overcurrent and thermal shutdown protection circuits built in 7) ON/OFF control via STBY pin 8) Ceramic output capacitor compatibility 9) Small surface mount TO252S-5 package Applications TVs, printers, DVD players, projectors, gaming devices, PCs, car audio/navigation systems, ETCs, communication equipment, AV products, office equipment, industrial devices, and more. Absolute Maximum RatingsTa25 Parameter Symbol Supply VoltageVCC-GND STBY-GND OUT-GND INV-GND Maximum Switching Current Power Dissipation Operating Temperature Storage Temperature
(*1) Do not exceed Pd, ASO, and Tjmax=150 (*2) Derated at 6.4mW/C over Ta=25
Ratings 36 36 36 5 1.5
(*1)
Unit V V V V A mW
Vcc VSTBY VOUT VINV Iout Pd Topr Tstg
800(*2) -40 to +85 -55 to +150
Operating Conditions(Ta=-40 to +85) Parameter Input Voltage Output Voltage Symbol VCC Vo Limit MIN 8.0 1.0 MAX 35.0 0.8x(VCC-IoxRon) Unit V V
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1/11
2009.05 - Rev.A
BD9870FPS
Electrical CharacteristicsUnless otherwise noted, Ta=25,Vcc=12V,Vo=5V,STBY=3V Limit Parameter Symbol Unit MIN TYP MAX Output ON Resistance Efficiency Switching Frequency Load Regulation Line Regulation Over Current ProtectionLimit INV Pin Threshold Voltage INV Pin Input Current STBY Pin Threshold Voltage STBYPin Input Current Circuit Current Stand-by Current Soft Start Time ON OFF Ron fosc VOLOAD VOLINE Iocp VINV IINV VSTBYON VSTBYOFF Istby Icc Ist Tss 80 810 1.6 0.99 2.0 -0.3 5 1 1.0 88 900 5 5 1.00 1 15 5 0 4 1.5 990 40 25 1.01 2 36 0.3 30 12 5 10 % kHz mV mV A V A V V A mA A ms STBY=3V INV=2V Io0.5A
Technical Note
Conditions
Vcc=20V, Io=0.5 to 1.5A Vcc=10 to 30V, Io=1.0A
VINV=1.0V
STBY0V
* This product is not designed to be resistant to radiation.
Block Diagram
VCC 1
VREF PWM COMP DRIVER
OSC STBY 5 STBY CTL LOGIC TSD OCP OUT 2
Error AMP 4
INV
SS FIN GND
Fig.1
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2/11
2009.05 - Rev.A
BD9870FPS
Package Dimensions
Technical Note
TO252S-5Unitmm Fig.2
Pin Description Pin No. 1 2 3
Pin Name VCC OUT OUT GND INV STBY
Function Input Power Supply Pin Internal Pch FET Drain Pin Internal Pch FET Drain Pin Ground Output Voltage Feedback Pin ON/OFF Control Pin
FIN 4 5
Normally OPEN
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3/11
2009.05 - Rev.A
BD9870FPS
Block Function Explanations VREF Generates the regulated voltage from Vcc input, compensated for temperature.
Technical Note
OSC Generates the triangular wave oscillation frequency (900kHz) using an internal resistors and capacitor. Used for PWM comparator input. Error AMP This block, via the INV pin, detects the resistor-divided output voltage, compares this with the reference voltage, then amplifies and outputs the difference. PWM COMP Outputs PWM signals to the Driver block, which converts the error amp output voltage to PWM form. DRIVER This push-pull FET driver powers the internal Pch MOSFET, which accepts direct PWM input. STBY Controls ON/OFF operation via the STBY pin. The output is ON when STBY is High. Thermal Shutdown (TSD) This circuit protects the IC against thermal runaway and damage due to excessive heat. A thermal sensor detects the junction temperature and switches the output OFF once the temperature exceeds a threshold value (175C). Hysteresis is built in (15C) in order to prevent malfunctions due to temperature fluctuations. Over Current Protection (OCP) The OCP circuit detects the voltage difference between Vcc and OUT by measuring the current through the internal Pch MOSFET and switches the output OFF once the voltage reaches the threshold value. The OCP block is a self-recovery type (not latch). Soft Start (SS) This block conducts soft start operations. When STBY is High and the IC starts up the internal capacitor begins charging. The soft start time is fixed at 5ms. Notes for PCB layout
C3 R2:1k 4 INV STBY 5 R1:4k
L1 1 VCC C2 GND FIN OUT 2 D1 C1 5.0V
Fig.3 * Place capacitors between Vcc and Ground, and the Schottky diode as close as possible to the IC to reduce noise and maximize efficiency. * Connect resistors between INV and Ground, and the output capacitor filter at the same Ground potential in order to stabilize the output voltage. If the patterning is longer or thin, it's possible to cause ringing or waveform crack.
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4/11
2009.05 - Rev.A
BD9870FPS
Technical Note
Application component selection and settings Inductor L1 A large inductor series impedance will result in deterioration of efficiency. OCP operation greater than 1.6A may cause inductor overheating, possibly leading to overload or output short. Note that the current rating for the coil should be higher than IOUT(MAX)IL. IoutMAX: maximum load current If you flow more than maximum current rating, coil will become overload, and cause magnetic saturation, and those account for efficiency deterioration. Select from enough current rating of coil which doesn't over peak current. (VCCVOUT) IL. = x VOUT x 1
fosc VCC L1 L1inductor value, VCCmaximum input voltage, VOUToutput voltage, ILcoil ripple current value, foscoscillation frequency If you make a point of efficiency, we will recommend C10-H5R(mitsumi).The efficiency will improve about 1-2%. Schottky Diode D1 A Schottky diode with extremely low forward voltage should be used. Selection should be based on the following guidelines regarding maximum forward current, reverse voltage, and power dissipation: The maximum current rating is higher than the combined maximum load current and coil ripple current (IL). The reverse voltage rating is higher than the VIN value. Power dissipation for the selected diode must be within the rated level. The power dissipation of the diode is expressed by the following formula: Pdi=Iout(MAX)xVfx(1-VOUT/VCC) IoutMAX: maximum load current, Vf: forward voltage, VOUT: output voltage, VCC: input voltage Output Capacitor C1 A suitable output capacitor should satisfy the following formula for ESR: ESRVL/IL VL : permissible ripple voltage, IL : coil ripple current Another factor that must be considered is the permissible ripple current. Select a capacitor with sufficient margin, governed by the following formula: IRMS =IL/23 IRMS: effective value of ripple current to the output capacitor, IL : coil ripple current Use ceramic capacitor over B characteristic of temperature. Except that, it is possible to cause abnormal movement of IC. It's depends on ambient temperature or output voltage setting Also it is possible to use Al electronic capacitor, but use it by enough confirmation. Input Capacitor C2 The input capacitor is the source of current flow to the coil via the built-in Pch FET when the FET is ON. When selecting the input capacitor sufficient margin must be provided to accommodate capacitor voltage and permissible ripple current. The expression below defines the effective value of the ripple current to the input capacitor. It should be used in determining the suitability of the capacitor in providing sufficient margin for the permissible ripple current. IRMSIOUTx (1VOUT / VCC)xVOUT / VCC IRMS : effective value of the ripple current to the input capacitor IOUT : output load current, VOUT: output voltage, VCC: input voltage Capacitor C3 This capacitor is utilized to stabilize the frequency characteristics, but is seldom used. However, if the phase margin is insufficient and oscillation is likely, connecting this capacitor may improve frequency stability. Resistor R1,R2 These resistors determine the output voltage: VOUT1.0Vx(1 + R1/R2) Select resistors less than 10k.
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5/11
2009.05 - Rev.A
BD9870FPS
Technical Note
Recommended Components (Example) Inductor L110H C6-K3LA (MITSUMI) Schottky Diode D1 RB050LA-30ROHM... use when VCC is less than 30V D2 RB050LA-40ROHM... use when VCC is greater than 30V Capacitor C110F(25V) ceramic cap GRM31CB31E106KA75L(murata) C24.7F(50V) ceramic cap GRM32EB31H475KA87L(murata) C3OPEN Recommended Components example 2...when the Duty ratio of output/input voltage is less than 10% Inductor L110H C6-K3LA (MITSUMI) Schottky Diode D1 RB050LA-30ROHM... use when VCC is less than 30V D2 RB050LA-40ROHM... use when VCC is more than 30V Capacitor C1100F(25V)Al electric capacitor UHD1E101MED(nichicon) C24.7F(50V) ceramic cap GRM32EB31H475KA87L(murata) C3OPEN Test Circuit
Vcc 1 +
OUT 2 SW2
GND FIN
INV 4 SW4
STB 5 SW5
Icc Vcc
A 1k 2k
A IINV VINV
A ISTB VST
f
+ Vo
V
SW6
Io
Fig.4
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6/11
2009.05 - Rev.A
BD9870FPS
Typical Performance CharacteristicsUnless otherwise noted, Ta=25,Vcc=12V,Vo=5V,STBY=3V
Technical Note
10 9
5.0
Io=0m A
4.5
STBY=0V
Circuit Current[mA]
7 6 5 4 3 2 1 0 0 10 20 30 40
Stand-by Current[uA]
8
4.0 3.5 3.0 2.5 2.0 1.5 1.0 0.5 0.0 -40 -15 10 35 60 85
VCC=8V VCC=12V VCC=24V
VCC=35V
Input Voltage[V]
Ambient Temperature[ ]
Fig.5 Circuit Current vs. Supply Voltageno load
Fig.6 Stand-by Current vs. Ambient temperature
Oscillator Frequency[kHz]
1100
1100
1000 950 900 850 800 750 700 0 10 20 30 40
Oscillator Frequency[kHz]
1050
1050 1000 950 900 850 800 750 700 -40 -15 10 35 60 85
Input Voltage[V]
Am bient Tem perature[ ]
Fig.7 Oscillator Frequency vs. Supply Voltage
Fig.8 Oscillator Frequency vs. Supply Voltage
1.05 1.04
7 6
Threshold Voltage[V]
Output Voltage[V]
1.03 1.02 1.01 1.00 0.99 0.98 0.97 0.96 0.95 5 10 15 20 25 30 35 40
5 4 3 2 1 0 0.0 1.0 2.0 3.0
Input Voltage[V]
STBY Input Voltage[V]
Fig.9 ErrorAmp Threshold Voltage vs. Supply Voltage
Fig.10 Output Voltage vs. STBY Pin Voltage
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7/11
2009.05 - Rev.A
BD9870FPS
Technical Note
3.0
Drain-Source Voltage[V]
2.5 2.0 1.5 1.0
VCC=8V
100 90
VCC=8V
Effeciency[%]
VCC=12V
80 70 60 50 40 30 20 10 0
VCC=12V VCC=24V
VCC=35V
0.5 0.0 0.0 0.5 1.0 1.5 2.0
0
500
1000
1500
2000
Output Current[A]
Load Current[mA]
Fig.11 Driver Drain-Source Voltage vs. Output Current
Fig.12 Efficiency vs. Load Current
7 6
5.05
Ro=50
5.04
Output Voltage[V]
Output Voltage[V]
5.03 5.02 5.01 5.00 4.99 4.98 4.97 4.96 4.95
VCC=35V VCC=12V
5 4 3 2 1 0 0 10 20 30 40
VCC=8V
0
500
1000
1500
Input Voltage[V]
Load Current[mA]
Fig.13 Output Voltage vs. Supply Voltage
Fig.14 Output Voltage vs. Load Current
Output Voltage[V]
6.0 5.5 5.0 4.5 4.0 3.5 3.0 2.5 2.0 1.5 1.0 0.5 0.0 0.0 0.5 1.0 1.5 2.0 2.5 3.0
STBY 0 3V 1V/div
Vo 2V/div
Ta=25 Ro=5 L:C10-H5R(MITSUMI)
Load Current[A]
Fig.15 Over Current Protection Characteristics
Fig.16 Output Start-up Characteristics
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8/11
2009.05 - Rev.A
BD9870FPS
I/O Equivalent Circuit Pin 1 (Vcc, GND) Pin 2 (OUT) Pin 4 (INV)
Technical Note
Pin 5 (STBY)
VCC
VCC
VCC
VCC
INV
STBY
OUT
GND
Operation Notes 1. Absolute Maximum Ratings Exceeding the absolute maximum ratings (i.e. supply voltage, temperature) may cause damage to the device and make it impossible to determine the failure mode (short/open). Therefore, when conditions exceeding the maximum ratings are anticipated, consideration should be given to preventive countermeasures (e.g. fuses). 2. Application circuit Although we can recommend the application circuits contained herein with a relatively high degree of confidence, we ask that you verify all characteristics and specifications of the circuit as well as performance under actual conditions. Please note that we cannot be held responsible for problems that may arise due to patent infringements or noncompliance with any and all applicable laws and regulations. 3. Operating conditions Proper operation is guaranteed under the recommended conditions/specifications. 4. GND voltage Ensure that the GND fin is connected and is at the lowest potential under any operating conditions, including transients. 5. Input supply voltage Ensure that the Vcc pin is connected to the supply voltage. 6. Thermal design Thermal designs should allow for sufficient margin for power dissipation under actual use. 7. Soldering During mounting ensure that the OUT, Vcc, and GND pins are not shorted with one another. Carefully note IC orientation. 8. Operation in strong electromagnetic field Operation in a strong electromagnetic field may cause malfunction. 9. Operation The IC will turn ON when the voltage at the STBY pin is greater than 2.0V and will switch OFF if under 0.3V. Therefore, do not input voltages between 0.3V and 2.0V. Malfunctions and/or physical damage may occur..
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9/11
2009.05 - Rev.A
BD9870FPS
10.This IC is a monolithic IC which (as below) has P+ substrate and between
Technical Note
the various pin. A P-N junction is formed from this P layer of each pin. For example the relation between each potential is as follows.(When GND > PinB and GND > PinA, the P-N junction operates as a parasitic diode.) Parasitic diodes can occur inevitably in the structure of the IC. The operation of parasitic diodes can result in mutual interference among circuits as well as operationfaults and physical damage. Accordingly, you must not use methods by which parasitic diodesoperate, such as applying a voltage that is lower than the GND(P substrate)voltage toan input pin. (PinB)

C

(PinA)
Resistance
B
Transistor (NPN) E GND N
P N N
P
P N N
P N
P
P N
P substrate Parasitic diode (PinA) GND
P substrate GND
Parasitic diode (PinB)

C

Parasitic diode GND Simplified structure of a Bipolar IC Other adjacent components Power Dissipation
B E GND Parasitic diode
W 5 No heat sink 2 layer PCB (Copper laminate area 15 mmx15mm) 2 layer PCB (Copper laminate area 70 mmx70mm)
4 POWER DISSIPATION [Pd] 3.50W
3
2
1.85W
1
0.80W
0 0 25 50 75 85 100 125 AMBIENT TEMPERATURE [Ta]
*When mounted on a 70mmx70mmx1.6mm board
150
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10/11
2009.05 - Rev.A
BD9870FPS
Ordering part number
Technical Note
B
D
9
Part No.
8
7
0
F
P
S
-
E
2
Part No.
Package FPS = TO252S-5
Packaging and forming specification E2: Embossed tape and reel (TO252S-5)
TO252S-5
C0.5
1.50.2
6.50.2 +0.2 5.1-0.1 FIN
1.20.1 0.270.1

Tape Quantity Embossed carrier tape 2000pcs E2
The direction is the 1pin of product is at the lower left when you hold
5.50.2
9.50.3
3
0.71
1
2
0.8
4
5
4 +6 -4 0.270.1
S 0.60.2
M
0.350.1
1.27
0.270.1 0.08 S
0.08
1.00.2 2.50.15
Direction of feed
( reel on the left hand and you pull out the tape on the right hand
)
1pin
Direction of feed
(Unit : mm)
Reel
Order quantity needs to be multiple of the minimum quantity.
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11/11
2009.05 - Rev.A
Notice
Notes
No copying or reproduction of this document, in part or in whole, is permitted without the consent of ROHM Co.,Ltd. The content specified herein is subject to change for improvement without notice. The content specified herein is for the purpose of introducing ROHM's products (hereinafter "Products"). If you wish to use any such Product, please be sure to refer to the specifications, which can be obtained from ROHM upon request. Examples of application circuits, circuit constants and any other information contained herein illustrate the standard usage and operations of the Products. The peripheral conditions must be taken into account when designing circuits for mass production. Great care was taken in ensuring the accuracy of the information specified in this document. However, should you incur any damage arising from any inaccuracy or misprint of such information, ROHM shall bear no responsibility for such damage. The technical information specified herein is intended only to show the typical functions of and examples of application circuits for the Products. ROHM does not grant you, explicitly or implicitly, any license to use or exercise intellectual property or other rights held by ROHM and other parties. ROHM shall bear no responsibility whatsoever for any dispute arising from the use of such technical information. The Products specified in this document are intended to be used with general-use electronic equipment or devices (such as audio visual equipment, office-automation equipment, communication devices, electronic appliances and amusement devices). The Products specified in this document are not designed to be radiation tolerant. While ROHM always makes efforts to enhance the quality and reliability of its Products, a Product may fail or malfunction for a variety of reasons. Please be sure to implement in your equipment using the Products safety measures to guard against the possibility of physical injury, fire or any other damage caused in the event of the failure of any Product, such as derating, redundancy, fire control and fail-safe designs. ROHM shall bear no responsibility whatsoever for your use of any Product outside of the prescribed scope or not in accordance with the instruction manual. The Products are not designed or manufactured to be used with any equipment, device or system which requires an extremely high level of reliability the failure or malfunction of which may result in a direct threat to human life or create a risk of human injury (such as a medical instrument, transportation equipment, aerospace machinery, nuclear-reactor controller, fuel-controller or other safety device). ROHM shall bear no responsibility in any way for use of any of the Products for the above special purposes. If a Product is intended to be used for any such special purpose, please contact a ROHM sales representative before purchasing. If you intend to export or ship overseas any Product or technology specified herein that may be controlled under the Foreign Exchange and the Foreign Trade Law, you will be required to obtain a license or permit under the Law.
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