TDA5345HT 데이터 시트보기 (PDF) - Philips Electronics

부품명

상세내역

제조사

TDA5345HT

5 V spindle & VCM driver combo

Philips Electronics 

Philips Semiconductors

5 V spindle & VCM driver combo

Preliminary specification

TDA5345HT

When the 6-bit DAC is used for the spindle, the LSB current is set externally, by means of a 33 kΩ resistor (to have a

very good absolute accuracy). The Spindle Current limit is then set by 31 steps of 20 mA. Please note that only the

positive codes of the 6-bit DAC can be used, so only (25 - 1) = 31 steps can be defined.

Table 8 Spindle Start-up current limit according to the spindle 6-bit DAC code :

INPUT CODE

000000

000001

011111

SPINDLE START-UP CURRENT

0 mA

20 mA

620 mA

When the 6-bit DAC is used for the VCM section, the LSB current is set by an internal resitor to have a good matching

with the 2 internal resistors used to set the VCM loop Gain. The VCM current offset is set by steps of :

IVCMOffset (LSB) = 1----.--6-R--1--S-3---e--⋅-n--1s---e0----–--3- ( A)

(4)

Table 9 VCM current offset according to the spindle 6-bit DAC code (assuming that RSense = 1 Ω, 1 LSB = 1.613 mA) :

INPUT CODE

VCM OFFSET CURRENT

011111

000000

1111111

100001

100000

+50 mA

0 µA

-1.613 mA

-50 mA

-50 mA

VCM driver

The VCM is a linear, AB class type with both low-side and high-side drivers configured as a H-bridge. The zero-current

reference voltage for the VCM loop is internally set at Vdd5/2=2.5 V. The sense resistor Rsense enables the VCM current

to be measured through the sense amplifier. The gain of the sense amplifier is internally set to typically 3. The output

VcmSenseOut is given by the following equation:

VcmSenseOut= 3 × (VcmSenseInP – VcmSenseInM) + VcmRef

(5)

Figure 14 presents the VCM sense amplifier.

VcmRef

18

IVCM

23

VcmSenseInP

R

3R

+

R = 10 kΩ

22

VcmSenseInM

1999 June 10

R

-

3R

Fig.11 VCM sense amplifier

19

Share Link: