BD9121GUL - ROHM Co., Ltd.

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STRUCTURE Silicon Monolithic Integrated Circuit

PRODUCT NAME 1ch DC／DC Converter Controller IC with Built-in Synchronous Rectifier

TYPE

BD9121GUL

FEATURES ・Output Voltage：Fixed(1.2V, 1.3V, 1.4V), Output Current：0.3A

・Fast transient response with current mode PWM control system

・High efficiency with sy nchronous re ct ifier

○ABSOLUTE MAXIMUM RATING（Ta=25℃）

Parameter Symbol Limit Unit

Supply Voltage VCC -0.3～+7 *1 V

PVCC -0.3～+7 *1 V

SEL Voltage SEL -0.3～+7 V

SW・ITH Voltage SW, ITH -0.3～+7 V

SW Output Current ISW 0.5 *1 A

Power Dissipation 1 Pd1 660 *2 mW

Operating Temperature Range Topr -25～+85 ℃

S torage Temperature Range Tstg -55～+150 ℃

Maximum Junction Temperature Tjmax +150 ℃

*1 Pd, ASO, and Tjmax=150℃ should not be exceeded.

*2 Derating is 5.28mW/℃ for temperatures above Ta=25℃ (when mounted on 50mm×58mm×1.6mm glass epoxy PCB).

○OPERATING CONDITIONS（Ta=-25～+85℃）

Parameter Symbol Min.

Typ. Max. Unit

Supply Voltage VCC 2.55 3 3.6 V

PVCC 2.55 3 3.6 V

SW Average Output Current ISW - - 0.3*3 A

*3 Pd and ASO should not be exceeded.

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○ ELECTRICAL CHARACTERISTICS (Unless otherwise specified, Ta=25℃, VCC=PVCC=3V, VOUT=1.3V）

Parameter Symbol Limit Unit Condition

Min. Typ. Max.

Bias Current ICC - 400 640

μA

Output Voltage1 VOUT1 -2 - +2 %

Output Voltage2 VOUT2 -3 - +3 %

Ta=-25～85℃

Oscillation Frequency1 FOSC1 2.4 3 3.6 MHz

Oscillation Frequency2 FOSC2 2.1 3 3.9 MHz

Ta=25～85℃

Pch FET ON Resistance RONP - 0.3 0.6

Ω PVCC=3V

Nch FET ON Resistance RONN - 0.2 0.4 Ω PVCC=3V

ITH Sink Current ITHSI 10 20 - μA VOUT=2V, SEL=OPEN

ITH Source Current ITHSO 10 20 - μA VOUT=0.8V, SEL=OPEN

UVLO Threshold Volt age VUVLO1 2.1 2.25 2.4 V

VCC=3→0V

UVLO Release Voltage VUVLO2 2.12 2.3 2.5 V

VCC=0→3V

Soft Start Time TSS 25 50 100

μs

Timer Latch Time TLATCH 0.68 1.36 2.72 ms

SCP/TSD

Operational Mode

Output Short circuit

Threshold Voltage VSCP - 0.65 1 V

VOUT=1.3→0V,

SEL=OPEN

○PHYSICAL DIMENSION ○BLOCK DIAGRAM・APPLICATION CIRCUIT

VCSP50L2 (UNIT:mm)

9 1 2 1

Lot No.

Input

PVCC

PGND

GND

Output

Gm Amp L

VCC

OSC

UVLO

TSD

4.7

VCC

CLK

SLOPE

Current

Comp

Soft

Start

Current

Sense/

Protect

Driver

Logic

VREF

ITH

VOUT

RITH CITH

SCP

SEL

4.7μF

10Ω

0.1

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○PIN DISTRIBUTION [Bottom View]

B2 PVCC

B3 VCC

B4 VOUT

PGND

A2 GND

A3 SEL

A4 ITH

○SETTING THE OUTPUT VOLTAGE ○PIN No.・PIN NAME

SEL Output Voltage〔V〕 PIN No. PIN NAME

GND 1.2 A1 PGND

OPEN 1.3 A2 GND

VCC 1.4 A3 SEL

※Cannot switch in operational mode. A4 ITH

B1 SW

B2 PVCC

B3 VCC

B4 VOUT

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○NOTES FOR USE

(1) Absolute maximum rating

Although the quality of this IC is rigorously controlled and will function properly in normal operating c onditions, the IC ma y

be destroyed when applied voltage or operating temperature exceeds its absolute maximum rating. Because short mode

or open mode cannot be specified when the IC is destroyed, it is important to take physical safety measures such as

fusing if a special mode in excess of absolute rating limits is to be implemented.

(2) GND potential

Make sure the potential for the GND pin is always kept at the minimum, regardless of the operating mode. In addition,

verify that the GND voltage is lower than the potential of all terminals except SW, PGND and GND in all conditions,

including electric transient events.

(3) Thermal design

Do not exceed the power dissipation (Pd) of the package specification rating under actual operation. Provide sufficient

margin in the thermal design to account for the Pd expected in actual use.

(4) Short-circuits between pins and incorrect mounting position

When mounting the IC onto the s et PCB, be extremely careful about the orientation and position of the IC. The IC may

be destroyed if it is incorrectly positioned for mounting. Do not short-circuit between pins, or betwee n a pin and the power

supply or ground terminal. Note that introducing foreign matter in these paths will cause shorts and may damage the IC.

(5) Operation in strong electromagnetic fields

Use in strong electromagnetic fields may cause malfunctions. Use extreme caution with electromagnetic fields.

(6) ASO (Area of Safe Operation)

Do not exceed the maximum ASO parameter or the absolute maximum ratings of the output driver.

(7) TSD (Thermal Shutdown) circuit

This product is provided with a built-in thermal shutdown (TSD) circuit, which is activated when the IC chip temperature

rises to the threshold value. In this case, TSD automatically latches output OFF. Output is restored when UVLO is

deactivated. Note that the TSD circuit is provided for the exclusive purpose shutting down the IC in the presence of

extreme heat, and is not designed to protect the IC per se or guarantee performance when or after extreme heat

conditions occur. Therefore, do not operate the IC with the expectation of continued use or subsequent operation once the

TSD is activated.

(8) GND wiring pattern

When both a small-signal GND and high current GND are present, single-point grounding (at the standard point on the

circuit set board) is recommended. This will separate the small-signal and high current patterns, and serves to ensure that

the high current flow and wire impedance will not change the small-signal GND voltage. In the same way, care must be

taken to avoid wiring pattern fluctuations in any connected external component GND.

(9) Operation in supply voltage range

Circuit functionality is guaranteed within the operating ambient temperature, as long as the operation is within the supply

voltage range. The standard electrical characteristics cannot be guaranteed.

However, any variation in these values will be small, as long as the operation is within the supply voltage range.

(10) The application schematic presented above is an example of recommended circuit layout. Although the circuit example is

sound, actual circuit characteristics should be checked carefully before use. Be sure to allow sufficient margins to

accommodate variations between external devices and this IC when employing the depicted circuit with other circuit

constants modified. Both static and transient characteristics should be considered in establishing these margins. When

switching noise is substantial and may impact the system, a low pass filter should be inserted between the Vcc and PVcc

pins, and a Schottky barrier diode established between the SW and PGND pins.

(11) Overcurrent protection circuit/Output short protection circuit

The overcurrent protection circuit is built into output, and functions as the current limit.

Note that if the protection circuit operates more than a specified time period (when the output short-circuit protection

circuit detects a load short or other similar state) the output will be latched OFF.

Output is restored when UVLO is deactivated. Although the protection circuits effectively prevent IC destruction under

fault conditions, they should not be employed continuously.

R1010

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