TK65910 Ver la hoja de datos (PDF) - Toko America Inc

Número de pieza

componentes Descripción

Fabricante

TK65910

SMALL EL LAMP DRIVER

Toko America Inc  

TK6591x

APPLICATION INFORMATION

LOW VOLTAGE SPLIT SUPPLY APPLICATION

The split power supply application of this EL driver IC is a circuit configuration (see Figure 4) in which the VCC IC power

(Vcontrol) is separated or split away from the main power input (Vpower) supplying current to the inductor.

CEL

5 nF

EL +

HV

EL -

VCC

GND

Vcontrol

from

2.7 to 6 V

max. 200 µA

IND

Vpower

L1

from

0.9 to 20 V

C1

D1

22 nF

FIGURE 4: SPLIT SUPPLY APPLICATION CIRCUIT

The voltage supplied to the VCC pin of the IC (Vcontrol) needs to be maintained in the 2.7 V to 6.0 V range, but the current

draw on this power supply rail of the system would be very small (under 200 µA). This Vcontrol can be used to turn on and

off the EL lamp driver, which permits the Vpower to be connected to the battery or other power source directly with the

least amount of resistance in the power path as possible.

Now with the VCC power for the IC (Vcontrol) being supplied from a different source, the main power (Vpower) can be any

voltage between 0.9 V and 20 V. But it is critical to properly select the inductor such that the proper peak current

regulation is maintained over the input voltage operating range of the converter.

If the inductor value is too large the current will rise too slowly and not have time to reach its set peak current trip point

at low input voltages, but at high input voltage the current might rise too quickly and overshoot the set peak current trip

point.

The primary low voltage battery applications for this part are in a single cell or a dual cell alkaline system (such as a pager

or PDA). These systems are assumed to have a minimum useable input voltage of 0.9 V for the single cell system and

1.8 V for the dual cell system.

For low converter input voltages (0.9 V and 1.8 V minimum input voltages), the following Table 5 shows the recommended

maximum inductance value for a given device part number (therefore a given frequency of operation) and a minimum

input voltage. Each cell in the table gives three inductance values; each value (in µH) corresponds to each type of

specialized Toko EL driver inductors (D31FU, D32FU, and D52FU types of Toko inductors).

Page 14

May 2000 TOKO, Inc.

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