PACKAGE CODES

PO

=

Small Outline Integrated Circuit (SOIC) SS

=

Shrink Small Outline Package (SSOP)

CIRCUIT OPERATION

The VM3200 addresses up to four 2-terminal, thin-film or MIG recording heads, providing switched write current in the write mode, or data amplification in the read mode. Head selection and mode control are determined by the head select lines, HS 1, HS2 and mode control lines, CS,

RIW as

shown in Tables 1 and 2. Internal resistor pullups, provided on the

CS

and

RIW

lines, will force the device into a non-write condition if either control line opens up. The part's operation over a wide range of induc-tive loads makes it suitable for two-terminal MIG heads also.

Write Mode

In write mode, the VM3200 acts as a write current switch with the write unsafe (WUS) detection circuitry activated. When switching from read-to-write mode, write current flows into the

"X" head port. Write current is toggled between the X and Y sides of the selected head in each high to low transition on the write data flip-flop (WDFF).

VTe Inc., 2800 East Old Shakopee Road, Bloomington, MN 55425,612·853·5100

The write current magnitude is determined by an extemal resistor (RWC) connected between the WC pin and ground. An internally generated reference voltage is present at the WC pin.

The magnitude of the write current is:

where,

Iw

=

Kw/Rwe

=

25/Rwe

Iw

=

Write Current Kw

=

Write Current Constant Rwe

=

Write Current Set Resistor

Power supply fault protection ensures data security on the disk by disabling the write current source during a power supply volt-age fault or by supply power up/down conditions. Additionally, the write unsafe (WUS) detection circuitry will flag any of the conditions listed below, as a high level on the WUS line. Two negative transitions on the WDI pin, after the fault is corrected, may be required to clear the WUS line. Write unsafe detect conditions:

• No write current

• WDI frequency too low

• Read or sleep mode

In write mode, the VM3200 provides 5 Vp-p differential head voltage swing with 3.3-volt supply that allows the write current to swing faster. This results in faster rise/fall times and improved writer performance.

Read Mode

In read mode, the VM3200 acts as a low-noise differential amplifier for signals coming off the disk. The write current gen-erator and write unsafe circuitry is deactivated. The RDX, RDY pins are emitter follower outputs and are in phase with "X" and .Y" head ports. These outputs should be AC coupled to the load.

The RDX, RDY common mode output voltage is constant, mini-mizing the transient between read and write mode, thereby, substantially reducing the recovery time in the pulse detector cir-cuit connected to these outputs.

Sleep Mode

When CS is high, initially all circuitry is shut down so that power dissipation is reduced to 0.7 mW in the sleep mode.

Switching the

CS

line low "wakes up" the chip and the device will enter the read or write mode, depending on the status of the RlWline.

Table 1: Head Select

HS1 HSO HEAD

0 0 0

0 1 1

1 0 2

1 1 3

VTe Inc., 2800 East Old Shakopee Road, Bloomington, MN 55425, 612·853·5100

Table 2: Mode Select

"B RlW MODE

0 0 Write/Awake

0 1 Read/Awake

1 X Sleep

PIN DESCRIPTIONS

NAME VO DESCRIPTION

HSO - HS1 1* Head Select: selects one of up to four heads

HOX - H3X

I/O X,Y Head Terminals HOY - H3Y

Write Data Input: TTL input signal, WDI 1* negative transition toggles direction

of head current

Chip Select: high level signal puts CS I chip in sleep mode, low level wakes

chip up

Read/Write Select: high level Rm 1* selects read mode, low-level selects

write mode

Write Unsafe: open collector output:

WUS 0* high level indicates writes unsafe condition

WC Write Current Adjust: a resistor adjusts level of write current RDX- RDY 0 Read Data Output: differential

output data

VCC +3.3V Supply**

GND Ground

* May be wire-OR'ed for multi-chip usage.

** Although both

vec

connections are recommended, only one connection is required as both are connected internally.

2-91

~~. ~.~

_~~,

.. ~ VM3200

DC CHARACTERISTICS Recommended operating conditions apply unless otherwise spepified.

PARAMETER SYM CONDmONS MIN

Read Mode

Power Supply Current Icc Write Mode

Idle Mode Read Mode

Power Dissipation PD Write Mode, Iw = 15mA Idle Mode

Input High Voltage VIH 2

Input Low Voltage VIL -0.3

Input High Current IIH VIH=2.7V -400

Input Low Current IlL VIL = 0.4V -1

WUS Output Low Voltage VOL IOL= 4.0mA WUS Output High Current IOH VoH =3.3V VCC Value for Write Current Turn

IH <0.2mA Off

Note 1: Typical values are given at T A = 25°C.

TYP MAX UNITS

(Note 1)

33 47

30+ 35+

1.3751w 1.3751w mA

0.3 TBD

120 170

165 200 mW

0.7 1.3

5.5 V

0.8 V

+1

ItA

+20

ItA

0.5 V

100

ItA

2.5 V

2-92 VTC Inc.: 2800 East Old Shakopee Road, Bloomington, MN 55425, 612-853-5100

READ CHARACTERISTICS Recommended operating conditions apply unless otherwise specilied, CL (RDX, ROY) < 20pF, RL (RDX, ROY)

=

1 kn.

PARAMETER SYM CONDmONS MIN

TYP

_{MAX UNITS}

(Note 1)

260 300 340

Differential Voltage Gain Av VIN = 1 mVrms, 1 MHz 170 200 330 VN

120 150 180

-1dB IZsI < 50, VIN = 1mVp-p 25 40

Bandwidth BW MHz

-3dB IZsI < 50, VIN = 1mVp-p 35 60

Input Noise Voltage ein BW = 17M Hz, LH = 0, RH = 0 0.48 TBD nV/-JRZ

VIN = 1 mVp-p, 1 = 5MHz, standard 20 TBD Differential Input Capacitance CIN

12

pF

VIN = 1mVp-p, 1 = 5MHz, low TBD

Differential Input Resistance RIN VIN = 1mVp-p, 1 = 5MHz 380 1000 pF

Dynamic Range DR AC input where Av is 90% 01 gain 2 4 mVrms

at 0.2mVrms input

Common Mode Rejection Ratio CMRR VIN = 100mVp-p @ 5MHz 50 73 dB

Power Supply Rejection Ratio PSRR 1oomVp-p @ 5MHz on Vee 45 70 dB

Channel Separation CS Unselected channel driven with

45 60 dB

20mVp-p @ 5MHz

Output Offset Voltage Vos -300 25 +300 mV

Single-Ended Output Resistance RSEO 50 0

Output Current 10 AC coupled load, RDX to ROY ±1.5 rnA

Note 1: Typical values are given at T A

=

25°C.

VTC Inc., 2800 East Old Shakopee Road. Bloomington, MN 55425. 612-853-5100 2-93

WRITE CHARACTERISTICS Recommended operating conditions apply unless otherwise specified, LH = 111H, RH = 300, Iw = 15mA, fDATA = 5MHi.

PARAMETER SYM CONDmONS MIN·

TYP

_{MAX UNITS}

(Note 1)

WC Pin Voltage Vwe 1.114 V

Vee=3V 22

Iwe to Head Current Gain AI mA/mA

Vee=5V 24.7

Kw = (Vwcl(AI), Vee = 3V 23 25 27

Write Current Constant Kw V

Kw = (Vwcl(AI), Vee = 5V 27.5 28

Write Current Range Iw 1 < Rwe < 12.51<0 2 25 mA

Write Current Tolerance A1w Iw=2-25mA -8 +8 "10

Open head, Vee = 3V 5

Differential Head Voltage Swing VDH Vp-p

Open head, Vee = 5V 9

WDI Transition Frequency for Safe

fDATA WUS=low 1 MHz

Condition

Differential Output Capacitance COUT 20 pF

Differential Output Resistance ROUT 3200

a

Unselected Head Current IUH Iw= 15mA 0.15 0.5 mA(pk)

RDX, ROY Common Mode Output

VeM 1.6 V

Voltage

Note 1: Typical values are given at T A = 25°C.

2-94 VTe Inc .• 2800 East Old Shakopee Reed. Bloomington. MN 55425.612-853-5100

SWITCHING CHARACTERISTICS Recommended operating conditions apply unless otherwise specified; Iw = 15mA, fOATA = 5MHz, I:.H = 11tH, RH = 300, CL (RDX, RDY) ~ 20pF (see Figure 1).

PARAMETER

SYM

RIW

Read to Write Delay tRW RIW Write to Read Delay tWR

CS

Unselect to Select Delay tlR CS Select to Unselect Delay tRI HSO, HS1 any Head Delay tHs WUS Safe to Unsafe Delay t01 WUS Unsafe to Safe Delay t02 Head Current Propagation t03 Head Current Asymmetry ASYM

Head Current Rise/Fall Time t,ltt

Dans le document Gain of ~ (Page 155-160)