BH6629BFS [ROHM]

Read /Write amplifier for FDD; 读/写放大器FDD


型号：	BH6629BFS
厂家：	ROHM
描述：	Read /Write amplifier for FDD 读/写放大器FDD 放大器
文件：	总14页 (文件大小：268K)
中文：	中文翻译
下载：	下载PDF数据表文档文件

Magnetic disk ICs

Read / Write amplifier for FDD

BH6629BFS

The BH6629BFS, a read/write IC designed for floppy disk drives, has a recording system that puts top priority on saddle

margin. Offers multi-step switching of write current, while density and inner track/outer track edge are switched internal-

ly.

FApplications

Floppy disk drives (1MB and 2MB drives)

FFeatures

1) Internal active filter switch.

2) Time domain filter (with internal switching based on

transfer rate).

3) Internal switching of write current density and inner

track/outer track.

FAbsolute maximum ratings (unless otherwise noted, Ta = 25_C)

FRecommended operating conditions (Ta = 25_C)

563

Magnetic disk ICs

BH6629BFS

FBlock diagram

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Magnetic disk ICs

BH6629BFS

FPin descriptions

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Magnetic disk ICs

BH6629BFS

566

Magnetic disk ICs

BH6629BFS

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Magnetic disk ICs

BH6629BFS

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Magnetic disk ICs

BH6629BFS

FElectrical characteristics (unless otherwise noted, Ta = 25_C, VCC = 5V)

Supply current

Low level voltage detection circuit

Recovery time

569

Magnetic disk ICs

BH6629BFS

Preamplifier

Preamplifier/L.P.F/differentiator (B.P.F)

570

Magnetic disk ICs

BH6629BFS

Comparator and waveform shaping

Write circuit

Erase output

571

Magnetic disk ICs

BH6629BFS

Logic input

FMode table

Total filter peak frequency setting

f⁰= a/ (RRCC [kΩ +0.09) [kHz]

a = 391 1M outer track

468 1M inner track

777 2M outer track

786 2M inner track

732 outer track (with OPTION 1), OPTION 2

777 inner track (with OPTION 1)

TDF time constant setting

250 [kbps] : T = 939 RRCC [kΩ] +667 [ns]

500 [kbps] : T = 403 RRCC [kΩ] +474 [ns]

Write current setting

24.0

Iwr =

[mA]

RWCC [kΩ]

572

Magnetic disk ICs

BH6629BFS

FFilter characteristic

573

Magnetic disk ICs

BH6629BFS

FMeasurement circuit

FCircuit operation

(1) Read

the internal flip-flops, operating the write driver. The write

driver current is supplied by the write current generator,

but the externally set current can be controlled according

to density and by selecting inner track/outer track.

(3) Erase

The input signal from the head coils from each side of the

disc is amplified by the preamplifier and then differen-

tiated. The filter time constant can be set externally. After

differentiation, the differential output is input to the

comparator. The time domain filter detects zero cross,

andtheoutputisconvertedtoreaddata. Themonostable

multivibrator width can be set externally, while the read

data pulse width is a constant 400ns.

An open collector output pin is used, and the erase cur-

rent is set with a resistor between it and the head.

(4) Power supply

When the low level voltage detector detects a drop in the

supply voltage, writing and erasing are prohibited.

(2) Write

Input write data are converted to toggle movements by

574

Magnetic disk ICs

BH6629BFS

FOperation notes

(1) Use a short pattern for VCC, and a sufficiently wide

AGND and DGND. Keep the impedance between V^CC

and GND low by inserting a bypass capacitor.

(2) Use a pattern that will minimize interference be-

tween digital signals and the head.

FElectrical characteristic curves

575

Magnetic disk ICs

BH6629BFS

FExternal dimensions (Units: mm)

576

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