ROHM BD9870FPS Technical data

Single-chip Type with Built-in FET Switching Regulator Series

Simple Step-down Switching Regulator with Built-in Power MOSFET

BD9870FPS

● 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 Ratings（Ta＝25℃）

Parameter Symbol Ratings Unit Supply Voltage（VCC-GND） Vcc 36 V STBY-GND V OUT-GND V INV-GND V Maximum Switching Current Iout 1.5 Power Dissipation Pd 800 Operating Temperature Topr -40 to +85 ℃ Storage Temperature Tstg -55 to +150 ℃

(*1) Do not exceed Pd, ASO, and Tjmax=150℃ (*2) Derated at 6.4mW/°C over Ta=25℃

●Operating Conditions(Ta=-40 to +85℃) Parameter Symbol

Input Voltage VCC 8.0 35.0 V Output Voltage Vo 1.0 0.8×(VCC-Io×Ron) V

36 V

STBY

36 V

OUT

5 V

INV

MIN MAX

(*1)

(*2)

Limit

No.09027EAT26

Unit

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Technical Note

●Electrical Characteristics（Unless otherwise noted, Ta=25℃,Vcc=12V,Vo=5V,STBY=3V）

Parameter Symbol

MIN TYP MAX

Limit

Unit Conditions

Output ON Resistance Ron - 1.0 1.5 Ω Efficiency η 80 88 - % Io＝0.5A Switching Frequency fosc 810 900 990 kHz

Load Regulation ΔVOLOAD - 5 40 mV

Vcc=20V, Io=0.5 to 1.5A

Line Regulation ΔVOLINE - 5 25 mV Vcc=10 to 30V, Io=1.0A Over Current ProtectionLimit Iocp 1.6 - - A INV Pin Threshold Voltage VINV 0.99 1.00 1.01 V INV Pin Input Current IINV - 1 2 μA VINV=1.0V

STBY Pin Threshold Voltage

ON VSTBYON 2.0 - 36 V

OFF VSTBYOFF -0.3 - 0.3 V STBYPin Input Current Istby 5 15 30 μA STBY=3V Circuit Current Icc - 5 12 mA INV=2V Stand-by Current Ist - 0 5 μA STBY＝0V Soft Start Time Tss 1 4 10 ms

* This product is not designed to be resistant to radiation.

●Block Diagram

VCC

VREF

PWM

COMP

DRIVER

STBY

OSC

STBY

TSD

CTL

LOGIC

OCP

OUT

Error AMP

INV

FIN

GND

Fig.1

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●Package Dimensions

●Pin Description

Pin No. Pin Name Function

1 VCC 2 OUT

3※ OUT

FIN GND

4 INV 5 STBY

※Normally OPEN

Technical Note

TO252S-5（Unit：mm）

Fig.2

Input Power Supply Pin Internal Pch FET Drain Pin Internal Pch FET Drain Pin Ground Output Voltage Feedback Pin ON/OFF Control Pin

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●Block Function Explanations

・ VREF

Generates the regulated voltage from Vcc input, compensated for temperature.

・ 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 (175°C). Hysteresis is built in (15°C) 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.

Technical Note

●Notes for PCB layout

• 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.）

R2:1kΩ

R1:4kΩ

INV

VCC OUT

GND

FIN

STBY

Fig.3

5.0V

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(

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 I Iout（MAX）: maximum load current

(MAX)＋⊿IL.

OUT

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.

⊿IL

VCC－VOUT)

VOUT

VCC

fosc

L1：inductor value, VCC：maximum input voltage, VOUT：output voltage, ⊿IL：coil ripple current value, fosc：oscillation 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 (⊿I

・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)×Vf×(1-VOUT/VCC) Iout（MAX）: 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: ESR≦⊿VL/⊿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/2√3 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 co nfirmation.

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.

IRMS＝IOUT×√

(1－VOUT / VCC)×VOUT / 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 freque ncy 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:

VOUT＝1.0V×(1 + R1/R2)

Select resistors less than 10kΩ.

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＜Recommended Components (Example)＞

Inductor L1＝10μH ：C6-K3LA (MITSUMI) Schottky Diode D1 ：RB050LA-30（ROHM）… use when VCC is less than 30V

D2 ：RB050LA-40（ROH M）… use when VCC is greater than 30V

Capacitor C1＝10μF(25V) ：ceramic cap GRM31CB31E106KA75L(murata)

C2＝4.7μF(50V) ：ceramic cap GRM32EB31H475KA87L(murata)

C3＝OPEN

＜Recommended Components example 2＞…when the Duty ratio of output/input voltage is less than 10%

Inductor L1＝10μH ：C6-K3LA (MITSUMI) Schottky Diode D1 ：RB050LA-30（ROHM）… use when VCC is less than 30V D2 ：RB050LA-40（ROHM）… use when VCC is more than 30V Capacitor C1＝100μF(25V)：Al electric capacitor UHD1E101MED(nichicon)

C2＝4.7μF(50V) ：ceramic cap GRM32EB31H475KA87L(murata)

C3＝OPEN

●Test Circuit

Icc

Vcc

OUT

SW2

GND

FIN

1kΩ

ig.4

INV

SW4 SW5

2kΩ

STB

IINV

VINV

ISTB

VST

SW6

Technical Note

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]

] ]

Technical Note

●Typical Performance Characteristics（Unless otherwise noted, Ta=25℃,Vcc=12V,Vo=5V,STBY=3V）

9 8 7 6 5 4 3 2

Circuit Current[mA

1 0

0 10203040

Input Voltage[V]

Io=0mA

5.0

4.5

4.0

3.5

3.0

2.5

2.0

1.5

1.0

Stand-by Current [ uA

0.5

0.0

-40 -15 10 35 60 85

VCC=8V VCC=12V VCC=24V

STBY=0V

VCC=35V

A mbient Temperature[℃]

Fig.5 Circuit Current vs. Supply Voltage：no load Fig.6 Stand-by Current vs. Ambient temperature

1100 1050 1000

950 900 850 800 750

Osci llato r Frequen cy[ kHz

700

010203040

Input Voltage[V]

1100 1050 1000

950 900 850 800

Oscillator Frequency[kHz]

750 700

-40 -15 10 35 60 85

Ambient Temperature[℃]

Fig.7 Oscillator Frequency vs. Supply Voltage Fig.8 Oscillator Frequency vs. Supply Voltage

1.05

1.04

1.03

1.02

1.01

1.00

0.99

0.98

0.97

Threshold Voltage[V]

0.96

0.95 5 10152025303540

Input Voltage[V]

Fig.9 ErrorAmp Threshold Voltage vs. Supply Voltage Fig.10 Output Voltage vs. STBY Pin Voltage

Outpu t V oltage[V]

0.0 1.0 2.0 3.0

STB Y Inpu t Vo l tage[V]

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]

Technical Note

3.0

2.5

2.0

1.5

1.0

0.5

Drain-So u rce Voltage[V]

0.0

0.0 0.5 1.0 1.5 2.0

Outp u t Current[A]

VCC=8V

VCC=12V

VCC=35V

100

90 80 70 60 50 40 30

Effeciency[%

20 10

0 500 1000 1500 2000

VCC=8V

VCC=12V VCC=24V

Load Current[mA]

Fig.11 Driver Drain-Source Voltage vs. Output Current Fig.12 Efficiency vs. Load Current

Ro=50

Output Voltage[V]

0 10203040

Input Voltage[V]

5.05

5.04

5.03

5.02

5.01

5.00

4.99

4.98

Output Voltage[V]

4.97

4.96

4.95 0 500 1000 1500

VCC=35V

VCC=12V

VCC=8V

Load Current[mA]

Fig.13 Output Voltage vs. Supply Voltage

Fig.14 Output Voltage vs. Load Current

6.0

5.5

5.0

4.5

4.0

3.5

3.0

2.5

2.0

1.5

Outpu t V oltage[V]

1.0

0.5

0.0

0.0 0.5 1.0 1.5 2.0 2.5 3.0

Load Current [A]

STBY 0→3V 1V/div

Vo 2V/div

Ta=25

℃

Ro=5Ω L:C10-H5R(MITSUMI)

Fig.15 Over Current Protection Characteristics Fig.16 Output Start-up Characteristics

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Technical Note

●I/O Equivalent Circuit

Pin 1 (Vcc, GND) Pin 2 (OUT) Pin 4 (INV) Pin 5 (STBY)

VCC

GND

VCC

OUT

VCC

INV

STBY

VCC

●Operation Notes

1. Absolute Maximum Rat ings 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, includ ing 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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Technical Note

10.This IC is a monolithic IC which (as below) has P+ substrate and between

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.

●Power Dissipation

(PinA)

Parasitic diode

(PinA)

（W）

POWER DISSIPATION [Pd]

0 25 50 75 100 125

*When mounted on a 70mmx70mmx1.6mm board

Resistance

P substrate

GND

Parasitic diode

GND

③3.50W

②1.85W

①0.80W

(PinB)

～

＋

P＋

N N

Parasitic diode

～

Simplified structure of a Bipolar IC

Other adjacent components

①No heat sink ②2 layer PCB (Copper laminate area 15 mm×15mm) ③2 layer PCB (Copper laminate area 70 mm×70mm)

AMBIENT TEMPERA TURE [Ta]

(PinB)

P substrate

～

150

（℃）

Transistor (NPN)

～

GND

＋

P＋

Parasitic diode

GND

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●Ordering part number

B D 9 8 7 0 F P S - E 2

Part No.

TO252S-5

Part No.

6.5±0.2

C0.5

0.71

+0.2

5.1

−0.1

FIN

1.5±0.2

5.5±0.2

0.8

1.27

0.35±0.1

0.08 S

0.27±0.1

FPS = TO252S-5

Package

1.2±0.1

0.08

0.27±0.1

1.0±0.2

–4

0.27±0.1

0.6±0.2

9.5±0.3

2.5±0.15

(Unit : mm)

Embossed carrier tapeTape

Quantity

Direction of feed

2000pcs E2

The direction is the 1pin of product is at the lower left when you hold

( )

reel on the left hand and you pull out the tape on the right hand

Reel

1pin

Order quantity needs to be multiple of the minimum quantity.

∗

Packaging and forming specification

E2: Embossed tape and reel

(TO252S-5)

Technical Note

Direction of feed

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Notes

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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 specied 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 specied 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 par ties. ROHM shall bear no responsibility whatsoever for any dispute arising from the use of such technical information.

Notice

The Products specied in this document are intended to be used with general-use electronic equipment or devices (such as audio visual equipment, ofce-automation equipment, communication devices, electronic appliances and amusement devices).

The Products specied in this document are not designed to be radiation tolerant.

While ROHM always makes ef forts 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, re or any other damage caused in the event of the failure of any Product, such as derating, redundancy, re 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.

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ROHM BD9870FPS Technical data

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