XC9504B092DAL datasheet(11/53 Pages) TOREX

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XC9504

Series

■NOTES ON USE (Continued)

●Hint on application

1. Channel 1 (Step-Up) How to shut down the output voltage during standby mode

If the circuit configuration shown as an example of typical application circuits is used, voltage VIN will occur at VOUT1 when

the IC is in standby, the diode being bypassed.

This can cause circuits connected to VOUT1 to malfunction.

> Example of typical application circuit 1:

Set R1 so as to prevent leakage current of N-ch MOSFET 2.

> Example of typical application circuit 2: Power Ready Function

The combination of R 2, C 1, and the threshold

voltage of approximately 0.7 V of NPN Bip 1 is

used to produce a delay time between the

circuits being enabled and P-ch MOSFET 1

being switched on.

Delay time set to 20ms

ensures power to be made ready in a favorable

manner, as soft start of this product is

completed during the delay time.

Set Value (Example)

VOLTAGE (V)

R2 (kΩ)

C1 (μF)

2.5

430

0.15

3.3

470

0.18

5.0

430

0.33

Time to make power ready is calculated by the equation below.

Time = - R2 x C1 x Ln (1 - 0.7 / [ON / OFF Signal Voltage ]

Set R1 so as to prevent leakage current of NPN (Bip 1).

N-ch MOSFET 2 and the inverter enables power to be turned off quickly.

2. Channel 2 (Inverting): Soft start circuit

Channel 2 (inverting) is subject to the overshoot of output voltage 2 (VOUT2) at start-up.

It is possible to control the

overshoot of output voltage 2 (VOUT2), as shown by circuit example 1 in “Output Voltage Settings for Channel 2” in

“Function Settings.” In this circuit configuration, EN 1 and EN 2 are enabled (set to “H” level) simultaneously.

This lets

output voltage 1 (VOUT1) of channel 1 increase gently as soft start, thereby controlling the overshoot.

> Example of typical application circuit: Improved Soft start

This example is effective when EN 1 and EN 2 are enabled with different timings under light load condition (the coil current

being discontinuous).

VOUT1

SBD1

FB1

EN1

Pch

MOSFET1

Inside of

XC9504 IC

RFB11

RFB12

CL1

CFB1

Nch

MOSFET2

ON/OFF

signal

VOUT1

SBD1

FB1

EN1

Pch

MOSFET1

RFB11

RFB12

CFB1

CL1

NPN

Bip1

Nch

MOSFET2

Inside of

XC9504 IC

ON/OFF

signal

SBD2

VOUT1

FB2

Inside of

XC9504 IC

RFB21

CFB21

VOUT2

CL2

RFB22

EN2

ON/OFF

signal

Pch

MOSFET1

Nch

MOSFET2

Time to make soft start time is calculated by the equation below.

Timess2 = -RFB21

× CFB21 / Ln 1 –

Example)

When VOUT1 = 15V and VOUT2 = - 7.5V,

RFB21 = 59.6k

Ω, RFB22 = 100kΩ by the equation below.

VOUT2 = (0.9 - VOUT1) x (RFB21 / RFB22) + 0.9

When the light load, CFB21=0.1

μF or lower value can be used.

Therefore, when CFB21=0.027

μF,

Time_ss2 = 5.0ms and VOUT2 = 95% of setting value

(0.9-VOUT2)

×RFB22)

(VOUT1 – 0.9)

×RFB21)

3. Channel 2 (Inverting): Withstand voltage of transistor

The voltage applied between the drain and source is the sum of VIN and VOUT2.

Select a transistor with an absolute VDSS

rating that is suitable for your operating conditions. Example: The voltage applied across VDS of a transistor will be 20.0V if

VIN = 5.0 V and VOUT2 = -15.0 V. Under this condition, a transistor with VDSS higher than 20.0V should be selected.

(Use

a transistor with VDSS that is 1.5 times the applied voltage or more, as a standard.)

XC9504B092DAL Datasheet(PDF) 11 Page - Torex Semiconductor

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