ELM620BA 1.4MHz
high efficiency synchronous PWM step up DC/DC converter
■Pin configuration
SOT-26(TOP VIEW)
1
2
3
6
5
4
Pin No.
Pin name
SW
GND
FB
EN
VOUT
VIN
Pin description
1
2
3
4
5
6
Switch
Ground
Feedback
ON/OFF control (High enable)
Output
Input
■Pin assignment
1) SW (Pin 1) : Switch pin.
Connect inductor between SW and VIN. Keep these PCB trace lengths as short and wide as possible to reduce
EMI and voltage overshoot.
2) GND (Pin 2) : Signal and power ground.
Provide a short direct PCB path between GND and the (−) side of output capacitor(s).
3) FB (Pin 3) : Feedback input to gm error amplifier.
Connect resistor divider tap to this pin. The output voltage can be adjusted from 2.5V to 6V by :
R1
R2
Vout = 1.203V × (1 +
)
4) EN (Pin 4) : Logic controlled shutdown input.
EN = High: Normal free running operation, 1.4MHz typical operating frequency. EN = Low: Shutdown, quies-
cent current < 1μA. Output capacitor can be completely discharged through the load or feedback resistors.
5) VOUT (Pin 5) : Output voltage sense input and drain of internal synchronous rectifier MOSFET.
Bias is derived from Vout. PCB trace length from Vout to output filter capacitor(s) should be as short and wide
as possible.
6) VIN (Pin 6) : Battery input voltage.
The device gets its start-up bias from Vin. Once Vout exceeds Vin, bias comes from Vout. Thus, once operation
is started, it is completely independent from Vin and only limited by output power level and battery’s internal
series resistance.
Rev.1.0
10 - 2
ELM-TECH [ ELM Technology Corporation ]
