ROHM BD9673EFJ Technical data

Single-chip Type with Built-in FET Switching Regulators

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

BD9673EFJ

●Description

Output 1.5A and below High Efficiency Rate Step-down Switching Regulator Power MOSFET Internal Type BD9673EFJ mainly used as secondary side Power supply, for example from fixed Power supply of 12V, 24V etc, Step-down Output of

1.2V/1.8V/3.3V/5V, etc, can be produced. This IC has external Coil/Capacitor down-sizing through 300 kHz Frequency operation, inside Nch-FET SW for 45V “withstand-pressure” commutation and also, high speed load response through Current Mode Control is a simple external setting phase compensation system, through a wide range external constant, a compact Power supply can be produced easily.

●Features

1) Internal 200 mΩ Nch MOSFET

2) Output Current 1.5A

3) Oscillation Frequency 300kHz

4) Synchronizes to External Clock ( 200kHz～500kHz )

5) Feedback Voltage 1.0V±1.0%

6) Internal Soft Start Function

7) Internal Over Current Protect Circuit, Low Input Error Prevention Circuit, Heat Protect Circuit

8) ON/OFF Control through EN Pin (Standby Current 0 A Typ.)

9) Package: HTSOP-J8 Package

●Applications

For Household machines in general that have 12V/24V Lines, etc.

●Absolute Maximum Rating

Parameter Symbol Ratings Unit

No.12027ECT57

VCC-GND Supply Voltage BST-GND Voltage BST-Lx Voltage EN-GND Voltage Lx-GND Voltage FB-GND Voltage VC-GND Voltage SYNC-GND Voltage High-side FET Drain Current Power Dissipation Operating Temperature Storage Temperature Junction Temperature

(*1)During mounting of 70×70×1.6t mm 4layer board (Copper area:70mm×70mm).Reduce by 30.08mW for every 1℃ increase. (Above 25℃)

●Operating Conditions (Ta=25℃) Parameter Symbol

Power Supply Voltage VCC 7 － 42 V Output Voltage VOUT 1.0

(*2)Restricted by minimum on pulse typ. 200ns

VCC 45 V

VBST 50 V

⊿VBST 7 V

VEN 45 V

VLX 45 V VFB 7 V

VC 7 V

SYNC 7 V

IDH 2.0 A

Pd 3.76 Topr -40～+105 ℃ Tstg -55～+150 ℃

Tjmax +150 ℃

Min. Typ. Max.

(*2)

－ VCC×0.7 V

(*1)

Ratings

Unit

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●Electrical Characteristics (Unless otherwise specified, Ta=25℃,VCC=24V, Vo=5V, EN=3V) Parameter Symbol

Min. Typ. Max.

Limits

【Circuit Current】

Technical Note

Unit Conditions

Stand-by current of VCC

Circuit current of VCC

【Under Voltage Lock Out (UVLO)】

Detect Voltage

Hysteresis width

【Oscillator】

Oscillating frequency

Max Duty Cycle

【Error Amp】

FB threshold voltage

Input bias current

Error amplifier DC gain

Trans Conductance

Soft Start Time

Ist － 0 10 µA

Icc

－

1 2 mA

Vuv 6.1 6.4 6.7 V

Vuvhy

－

200 300 mV

fosc 270 300 330 kHz

Dmax 85 91 97 %

VFB 0.990 1.000 1.010 V

IFB -1.0 0 1.0 µA

700 7000 70000 V/V

VEA

110 220 440 µA/V

Tsoft 7 10 13 ms

VEN=0V

FB=1.2V

VFB=0V

IVC=±10µA, VC=1.5V

【Current Sense Amp】

VC to switch current transconductance

【Output】

Lx NMOS ON resistance

Lx pre-charge NMOS ON resistance

Over Current Detect Current

【CTL】

EN Pin Control voltage

ON OFF

EN Pin input current

【SYNC】

SYNC Pin Control voltage

High Low

SYNC Pin input current

SYNC falling edge to LX rising edge delay

◎ Not designed to withstand radiation.

5 10 20 A/V

RonH － 200 340 mΩ

RonL

－

10 17 Ω

Iocp 2.0 3.3 － A

VENON 2 － VCC V

VENOFF -0.3 － 0.8 V

REN 2.7 5.5 11 µA

VSYNCH 2.0 － 5.5 V VSYNCL -0.3 － 0.8 V

REN 6 12 24 µA

tdelay 200 400 600 ns

VEN=3V

VSYNC=3V

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●Pin Description

8765

Thermal Pad

Technical Note

No.

Name

Function

1 Lx Terminal for inductor

2 GND Ground pin

3 VC Error amplifier output

4 FB Inverting node of the trans conductance error amplifier

1 234

Fig.1 Pin Layout Diagram

●Block Diagram

ON/OFF

1.0

Soft

Start

+ +

TSD

shutdown

Error

ReferenceUVLO

VREF

Comparator

Oscillator

300kHz

5 SYNC

Input pin of an external signal for the device synchronized by external signal

6 EN Stand-by ON/OFF pin

7 BST Voltage Supply pin for High Side FET Driver

8 VCC Voltage input pin

VCC

REG

Sense

Current

RQ S

BST

200mΩ

10Ω

GND

SYNC

Fig.2 Block Diagram

VOUT

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●Block Description

1. Reference This block generates Error Amp standard voltage. Standard voltage is 1.0V.

2. REG This is a Gate Drive Voltage Generator and 5V Low saturation regulator for internal circuit power supply.

3. OSC This is a precise wave oscillation circuit with operation frequency fixed to 300 kHz fixed (self-running mode). To implement the synchronization feature connect a square wave (Hi Level: higher than 2V, Low Level: lower than

0.8V )to the SYNC pin. The synchronization frequency range is 200 kHz to 500 kHz. After connecting the rising edge of LX will be synchronized to the falling edge of SYNC pin signal after 3 counts. At the synchronization remove the external clock, the device transitions self-running mode after 7 microseconds.

4. Soft Start A circuit that does soft start to the output voltage of DC/DC comparator, and prevents rush current during start-up. Soft start time is set at IC internal, after 10 ms from starting-up EN pin, standard voltage comes to 1.0V, and output voltage becomes set voltage.

5. ERROR AMP This is an Error amplifier what detects output signal, and outputs PWM control signal. Internal Standard Voltage is set to 1.0V. Also, C and R are connected between the output (VC) pin GND of Error Amp as Phase compensation elements. (See p.11)

6. ICOMP This is a Voltage-Pulse Width Converter that controls output voltage in response to input voltage. This compares the Voltage added to the internal SLOPE waveform in response to the FET WS current with Error amplifier output voltage, controls the width of output Pulse and outputs to driver.

7. Nch FET SW This is an internal commutation SW that converts Coil Current of DC/DC Comparator. It contains 45V” with stand pressure” 200mΩ SW. Because the Current Rating of this FET is 2.0A included ripple current, please use at within 2.0A. The device has the circuit of over current protection for protecting the FET from over current. To detect OCP 2 times sequentially, the device will stop and after 13msec restart.

8. UVLO This is a Low Voltage Error Prevention Circuit. This prevents internal circuit error during increase of power supply voltage and during decline of power suppl y voltage. It monitors VCC pin voltage and internal REG voltage, and when VCC voltage becomes 6.4V and below, it turns off all output FET and turns off DC/DC comparator output and soft start circuit resets. Now this threshold has hysteresis of 200mV.

9. TSD This is a Heat Protect (Temperature Protect) Circuit. When it detects an abnormal temperature exceeding Maximum Junction Temperature (Tj=150℃), it turns off all output FET, and turns off DC/DC comparator output. When Temperature falls, it has/with hysteresis and automatically returns.

10. EN With the Voltage applied to EN Pin (6pin), IC ON/OFF can be controlled. When a Voltage of 2.0V or more is applied, it turns on, at open or 0V application, it turns off. About 550 kΩ pull-down resistance is contained within the pin.

Technical Note

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Technical Note

●Detailed Description

◇Synchronizes to External Clock

The SYNC pin can be used to synchronize the regulator to an exter nal system clock. To implement the synchronization feature connect a square wave to SYNC pin. The square wave am plitude must transition lo wer than 0.8V and higher than

2.0V on the SYNC pin and have an on time greater than 100 ns and an off time greater than 100 ns. The synchronization frequency range is 200 kHz to 500 kHz. The rising edge of the LX will be synchronized to the falling edge of SYNC pin signal after SYNC input pulse 3 count. At the synchronization, the external clock is removed, the device transitions self-running mode after 7 microseconds. If the function of the synchronization is not used, please connect SYNC pin to ground.

SYNC

SYNC_LATCH

Set the latch for synchronization

400nsec

about 7µsec

Fig.3 Timing chart at Synchronization

◇SOFT START

The soft start time of BD9763EFJ is determined by the DCDC operating frequency (self-run mode 300 kHz ⇒10ms). If synchronization is used at the time of EN=ON, The soft start time is restricted by SYNC pin input pulse frequency. SYNC pin input pulse frequency is fosc_ex kHz, the soft start time is expressed by below equation.

Tss = × 10 [ms]

300

fosc_ex

◇The case of not using the function of synchronization

Although the SYNC pin is pulled down by resistor in this

device, if the function of the synchronization is not used , it is recommended to connect SYNC pin to ground.

Fig.4 the method to disposal the SYNC pin without synchronization

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◇OCP operation

The device has the circuit of over current protection for protecting the FET from over current. To detect OCP 2 times sequentially, the device will stop and after 13msec restart.

VC voltage rising by

output connect to GND

OCP threshold

VC voltage discharged

by OCP latch

force the High side FET OFF

by detecting OCP current

(pulse by pulse protection)

output connect to GND

VOUT

OCP

set the OCP latch by detectin g

the OCP current 2 times sequencially

OCP_LATCH

Fig.5 Timing chart at OCP operation

Technical Note

OCP latch reset after 13 msec

(300ｋHz 4000 counts)

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