ROHM BA9756FS Datasheet

BA9756FS

Multimedia ICs

High-voltage control circuit for CRT
displays

BA9756FS

The BA9756FS is LSIs that control CRT anode voltage in multi-scan monitors and similar devices, using
a chopper-type voltage control circuit. The internal sawtooth wave generator circuit uses automatic gain control
(AGC) to enable coverage of a wide range from 30kHz to over 150kHz. The BA9756FS is equipped with an internal
high-precision voltage source featuring an output voltage precision of ± 0.7%.

Applications

!

CRT displays, HDTVs, others

Features

!

Block diagram

!

20119218317416515614713812911

CC

1V

V

1) Internal chopper-type voltage
control circuit.

2) Internal buffer circuit enables direct
drive of Power MOSFET for output
drive.

3) Internal high-precision voltage
source offers output voltage
precision of ± 0.7%.

Absolute maximum ratings

!

Parameter Symbol Limits Unit
Power supply voltage 1
Power supply voltage 2
Power dissipation
Operating temperature
Storage temperature

When mounted on a 70mm × 70mm × 1.6mm glass epoxy board.

*

1

Reduced by 7.5mW for each increase in Ta of 1˚C over 25˚C.

(Ta=25°C)

V

CC

1

V

CC

2

Pd
Topr
Tstg

18
20

1

*

750

- 25~+80

- 55~+125

CC

2

–

+

SAW GEN.

M / M

+
+

–

9.0V
REF

Buffer

GND

10

V
V

mW

˚C
˚C

Recommended operating conditions

!

Parameter Symbol UnitMax.Typ.Min.

CC

Power supply voltage 1
Power supply voltage 2

V
V

CC

1
2

(Ta=25°C)

11
11

-

-

17
17

V
V

Multimedia ICs

Pin descriptions

!

Pin No. Pin name Function

1

2
3

ERRIN

(error amplifier + input)

AGC

(constant for AGC)

N.C.

SAWOUT

4

(constant for

sawtooth wave)
5
6

N.C.

MMCR

(delay constant for

monostable multivibrator)

7

8
9

10

11

12

13
14

HDIN

(Hd pulse input)

VREF9

(Ref 9V output)

N.C.

GND

(Signal GND)

GND

(Power GND)

PWMOUT

(PWM output)

N.C.
V

CC

2

(Power V

DTC IN

15

(dead time

control input)

16
17

ERROUT

(error amplifier output)

N.C.

18 N.C. See
19

20

1 N.C. pin processing

*

In order to boost the thermal effect of the IC, we recommend connecting this to the GND or to an adjacent pin.

2

*

ERRREF

(error amplifier input)

CC

1

V

CC

(signal V

11 12 14

This is the recovery voltage input pin.
Capacitance should be determined taking into consideration the linearity at the minimum

oscillation frequency, and the response time when the frequency changes.

1

*

.

See
This is the output pin for optimized sawtooth waves, based on the maximum oscillation

frequency.
fMax120kHz C = 1000pF fMax100kHz C = 1200pF
fMax 80kHz C = 1500pF fMax 60kHz C = 2000pF

1

*

.

See
A charging resistance of 4.7kΩ or higher should be used.

The threshold level is 4.5V.

The threshold level is approximately 2.1V.

An output deviation of ± 0.7% is assured through trimming.

1

*

.

See
This may be shared with the power GND, but make sure sufficiently stable grounding

is provided.

This may be shared with the signal GND, but make sure sufficiently stable grounding
is provided.

CC

If a voltage of less than GND or higher than V

is applied because of external back
electromotive force, a protective diode should be inserted (
If the protector circuit and thermal shutdown circuit are tripped, output is fixed at high (V

level.

1

*

See

.

A decoupling capacitor should be positioned in the vicinity of this pin.

CC

)

The voltage input to this pin enables restriction of the PWM output duty.
The duty control is between 0V and 9V, and approximately 0% to 100% is enabled. At 0V,
however, restrictions apply.
The minimum pulse width for the PWM is 0.85µs (Typ. at 90kHz).

This is the output pin for the error amplifier.

1

*

See

.

1

*

.

This is the input pin for the reference voltage.

A decoupling capacitor should be positioned in the vicinity of this pin.

)

V

CC

2

BA9756FS

2

*

).

CC

)

TO FET gate

+

Multimedia ICs

Input / output circuits

!

1

ERRIN

BA9756FS

V

CC

V

CC

V

CC

2

AGC

Fig.1

V

CC

7

6

MMCR

HDIN

V

Fig.2

CC

4

SAW OUT

Fig.3 Fig.4