a8438eej-t Allegro MicroSystems, Inc., a8438eej-t Datasheet

a8438eej-t

Manufacturer Part Number

a8438eej-t

Description

A8438 Photoflash Capacitor Charger With Igbt Driver

Manufacturer

Allegro MicroSystems, Inc.

Datasheet

1.A8438EEJ-T.pdf (15 pages)

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BIAS

Features and Benefits

▪ Power with 1 Li+ or 2 Alkaline/NiMH/NiCAD batteries

▪ Adjustable output voltage

▪ >75% efficiency

▪ Three levels of switch current limit: 1.6, 1.8, 2.0 A

▪ Fast charge time

▪ Charge complete indication

▪ Integrated IGBT driver with trigger

▪ No primary-side Schottky diode needed

▪ Low-profile package (0.75 mm nominal height)

Package: 10 pin TDFN/MLP (suffix EJ)

A8438-DS, Rev. 2

Figure 1. Typical circuit with separate power supply to transformer

3.0 to 5.5 V

10 k

100 k

1.8 A (N.C.)

2.0 A

1.6 A

Approximate Scale 1:1

10 k

ILIM

DONE

CHARGE

TRIGGER

VIN

GND

0.1 μF

BATT

IGBTDRV

A8438

Two Alkaline/NiMH/NiCAD or one Li+ battery

or 1.5 to 5.5 V

Photoflash Capacitor Charger with IGBT Driver

4.7 μF

To IGBT Gate

Typical Applications

COUT

OUT

Description

The A8438 is a highly integrated IC that charges photoflash

capacitors for digital and film cameras. It also features an

integrated IGBT driver that facilitates the flash discharge

function and saves board space.

To charge the photoflash capacitor, the A8438 integrates a

40 V, DMOS switch that drives the transformer in a flyback

topology, allowing optimized design with tight coupling and

high efficiency. A proprietary control scheme optimizes the

capacitor charging time. Low quiescent current and low

shutdown current further improve system efficiency and

extend battery life.

Three levels of switch current limit are provided: 1.6, 1.8,

and 2.0 A. The level is determined by configuring the ILIM

pin as grounded, floating, or pulled up to IC supply voltage,

respectively.

The CHARGE pin enables the A8438 and starts the charging

of the output capacitor. When the designated output voltage

is reached, the A8438 stops the charging until the CHARGE

pin is toggled again. Pulling the CHARGE pin low stops

charging. The ¯ D ¯ ¯ O ¯ ¯ N ¯ ¯ E ¯ pin is an open-drain indicator of when

the designated output voltage is reached.

The A8438 can be used with two Alkaline/NiMH/NiCAD or one

single-cell Li+ battery connected to the transformer primary.

Connect the VIN pin to a 3.0 to 5.5 V supply, which can be

either the system rail or the Li+ battery, if used.

The A8438 is available in a very low profile (0.75 mm) 10-

terminal 3×3 mm MLP/TDFN package, making it ideal for

space-constrained applications. It is lead (Pb) free, with 100%

matte-tin leadframe plating.

BATT

Figure 2. Typical circuit with single power supply

One Li+ battery

or 3.0 to 5.5 V

10 k

100 k

1.8 A (N.C.)

2.0 A

1.6 A

10 k

ILIM

DONE

CHARGE

TRIGGER

VIN

GND

0.1 μF

IGBTDRV

A8438

4.7 μF

To IGBT Gate

A8438

COUT

OUT

Related parts for a8438eej-t

a8438eej-t Summary of contents

Page 1

Photoflash Capacitor Charger with IGBT Driver Features and Benefits ▪ Power with 1 Li Alkaline/NiMH/NiCAD batteries ▪ Adjustable output voltage ▪ >75% efficiency ▪ Three levels of switch current limit: 1.6, 1.8, 2.0 A ▪ Fast charge time ...

Page 2

... Description (continued) Applications include: ▪ Digital camera flash ▪ Film camera flash ▪ Cell phone flash ▪ Emergency strobe light Selection Guide Part Number A8438EEJTR-T *Contact Allegro for additional packing options Absolute Maximum Ratings Characteristic SW pin IGBTDRV pin FB pin All other pins ...

Page 3

... Output voltage feedback 10 ILIM Switch current limit setting; sets three discreet levels SW Control Logic 40 V DMOS Q SET CLR SET CMP1 CLR 1.2 V One-Shot Function Allegro MicroSystems, Inc. 115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000 www.allegromicro.com 3 ...

Page 4

... V – 3.3 V – 3.3 V – 3.3 V – IN Allegro MicroSystems, Inc. 115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000 www.allegromicro.com Typ. Max. Units – 5 – μA 0.01 1 μA 1.6 – A 1.8 2 ...

Page 5

... D ¯ ¯ O ¯ ¯ N ¯ ¯ E ¯ goes low, to signal the OUT is below V IN goes above V , another low-to-high transition at the CHARGE pin is UVLO above the V level. IN UVLO level when CHARGE goes high. UVLO Allegro MicroSystems, Inc. 115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000 www.allegromicro.com 5 ...

Page 6

... 200 Value 2.5 V 3.3 V 100 μ 200 Value 3.0 V 3.3 V 100 μ OUT I BATT t V OUT I BATT t V OUT I BATT t Allegro MicroSystems, Inc. 115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000 www.allegromicro.com 6 ...

Page 7

... V 3.3 V 100 μ 200 Value 4 100 μ 200 Value 5.0 V 3.3 V 100 μ OUT I BATT t V OUT I BATT t V OUT I BATT t Allegro MicroSystems, Inc. 115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000 www.allegromicro.com 7 ...

Page 8

... Photoflash Capacitor Charger with IGBT Driver Performance Characteristics 50 V 200 Value 2 770 mA 1.8 A 140 μ 200 Value 2.0 V 3.3 V 820 mA 2 140 μ OUT I BATT t V OUT I BATT t Allegro MicroSystems, Inc. 115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000 www.allegromicro.com 8 ...

Page 9

... IGBT Drive Timing Definition 50% 50 90% 10% Efficiency T = 25° 3 5.0 V BATT BATT 3.3 V BATT IN 150 200 250 V (V) OUT 90% 10% Allegro MicroSystems, Inc. 115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000 www.allegromicro.com = 5 300 9 ...

Page 10

... LOAD R 12 Ω gate Photoflash Capacitor Charger with IGBT Driver IGBT Drive Performance IGBTDRV V TRIGGER IGBTDRV V TRIGGER t Allegro MicroSystems, Inc. 115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000 www.allegromicro.com 10 ...

Page 11

... Figure 3. Sequencing of Timer mode and Fast Charging mode (time axis scale per division only partially discharged. In Fast Charging OUT , is less than approximately Timer OUT Fast Charging Mode Timer Mode Allegro MicroSystems, Inc. 115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000 www.allegromicro.com 11 ...

Page 12

... I , can be set to three levels by SWLIM Setting ILIM Pin (A) Connection 1.6 External ground 1.8 Float Pull supply voltage 2.0 with kΩ resistor may be adjusted during charging. SWLIM Allegro MicroSystems, Inc. 115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000 www.allegromicro.com 12 ...

Page 13

... X5R or X7R Fairchild Semiconductor BAV23S D1 (dual diode connected in series) TDK LDT565630T-041 4.7 μ 10.2 Primary R1, R2 1206 resistors 0603 resistor R4, R5 Pull-up resistors R6, R7 Pull-down resistors Allegro MicroSystems, Inc. 115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000 www.allegromicro.com (3) The trans- 13 ...

Page 14

... Murata Taiyo Yuden Chemi-Con Philips Semiconductor, Fairchild Semiconductor Vishay Yageo Yageo Asatech TDK TDK Tokyo Coil Engineering Tokyo Coil Engineering Allegro MicroSystems, Inc. 115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000 www.allegromicro.com (5) (6) , for the ¯ D ¯ ¯ O ¯ 14 ...

Page 15

... Allegro products are not authorized for use as critical components in life-support devices or sys tems without express written approval. The in for ma tion in clud ed herein is believed rate and reliable. How ev er, Allegro MicroSystems, Inc. assumes no re spon si bil i ty for its use; ...

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