BD8374HFP-M datasheet(9/29 Pages) ROHM

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Datasheet

BD8374HFP-M

BD8374EFJ-M

TSZ02201-0G1G0C700310-1-2

2013.08.06 Rev.001

www.rohm.com

TSZ22111・15・001

[s]

)

(

CRT_DIS1

CRT_CHA

CRT























[Hz]

f PWM





DON





(2)

CRT Ramp down Time T2

CRT ramp down time is defined by discharge period due to external capacity CCRT and resistance (RCRT + RD1).

Make sure that T2 is set at not smaller than Min. pulse width 100

μs(Min).

where:

RD1 is the CRT Terminal Discharge Resistance 1

Ω (Typ)

VCRT_CHA is the CRT Terminal Discharge ON Voltage

1.1V (Typ)

VCRT_DIS1 is the CRT Terminal Discharge ON Voltage 13.0V (Typ)

(3)

Dimming Frequency fPWM

PWM frequency is defined by T1 and T2.

(4)

ON Duty (DON)

Like the above, PWM ON duty is defined by T1 and T2.

(Ex) In case of fPWM = 518Hz and 6.7% Duty (Typ),

From fPWM=518Hz; T1 + T2 = 1 / fPWM = 1 / 518Hz = 1931

μs

From ON Duty = 6.7%; CRT ramp up time T1 is T1 = (T1 + T2) × 0.933 = 1801.6

μs

External capacity CCRT is;

CCRT = T1 × (ICRT /

∆VCRT) = 1800.7μs × 35μA / 1.9V ≒ 0.033μF

CRT ramp down time T2 is; T2 = (T1 + T2) × 0.067 = 129

μs

External resistance RCRT is;

RCRT = －T2 / (CCRT × ln(VCRT_CHA / VCRT_DIS)) － RD1 = －129usec / (0.033μF × ln(1.1 / 3.0) – 50Ω ≒ 3.9kΩ

In case where PWM signal is applied from external;

It is possible to directly input PWM signal from external microcomputer for Dimming.

Input PWM signal to CRT terminal. In that case, ’H’ level voltage of PWM signal should be equal to or higher than

VCRT_DIS2(4.0V(Typ)).

Figure 13. External Input of PWM Signal

VREF

IOUT

VIN

VIN-0.180V

(Typ)

GND

VIN_F

OSC

CRT

PWM Signal Input

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