A8739EEETR-T Allegro Microsystems Inc, A8739EEETR-T Datasheet

A8739EEETR-T

Manufacturer Part Number

A8739EEETR-T

Description

Photoflash Capacitor Charger

Manufacturer

Allegro Microsystems Inc

Type

Flash/Torchr

Datasheet

1.A8739EEETR-T.pdf (21 pages)

Specifications of A8739EEETR-T

Number Of Outputs

Internal Driver

Type - Primary

Flash/Torch

Voltage - Supply

Mounting Type

Surface Mount

Package / Case

8-UFDFN Exposed Pad

Operating Temperature

Voltage - Output

Frequency

Current - Output / Channel

Internal Switch(s)

Yes

Efficiency

75%

Topology

Lead Free Status / RoHS Status

Lead free / RoHS Compliant

Other names

620-1365-2

Current page: 1 of 21
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Features and Benefits

▪ Primary-side output voltage sensing; no resistor divider required

▪ Adjustable switch peak current limit up to 1.5 A with

▪ Option to fine-tune target voltage

▪ Ultra-small 2 × 2 DFN/MLP-8 package

▪ Integrated IGBT driver with internal gate resistors

▪ Low quiescent current draw (0.5 μA max. in shutdown mode)

▪ 1V logic (V

▪ Zero-voltage switching for lower loss

▪ >75% efficiency

▪ Charge complete indication

▪ Integrated 50 V DMOS switch

Package: 8-pin DFN/MLP (suffix EE)

Not to scale

8739-DS

single-wire programming through the CHARGE pin

Figure 1. Typical applications: (A) with single battery supply and (B) with separate bias supply

VIN_VDRV

CHARGE

TRIG

(min)) compatibility

2 mm × 2 mm, 0.60 mm height

VBAT

V IN_VDRV

BAT

Control

IGBT Driver

Block

GND

Battery Input

2.3 to 5.5 V

(A)

Ultra-Small Mobile Adjustable Xenon Photoflash

DONE

VOUT Detect

sense

DONE

GATE

IGBT Gate

COUT

100F

315 V

Typical Applications

VPULLUP

100 kΩ

Capacitor Charger with IGBT Driver

The Allegro

Description

to provide an ultra-small solution with flexibility to adjust

both charging current limit and output voltage target. By using

primary-side voltage sensing, the need for a secondary-side

resistive voltage divider is eliminated. This has the additional

benefit of reducing leakage currents on the secondary side of

the transformer. Target output voltage is primarily determined

by the transformer turns ratio, but it can be further adjusted (in

steps of –5 V each) using an external resistor. This enables better

output accuracy, as well as greater flexibility in the selection of

transformers.

To extend battery life, the A8739 features very low supply

current draw (0.5 μA max in shutdown mode and 10 μA in

standby mode). The switch current limit can be programmed

from 0.45 to 1.5 A in 16 steps with single wire interface,

through the CHARGE pin.

external component count. The charge and trigger voltage

logic thresholds are set at 1 V

implementing low-voltage control logic.

The A8739 is available in an 8-contact 2 mm × 2 mm

DFN/MLP package with a 0.60 maximum overall package

height, and an exposed pad for enhanced thermal performance.

It is lead (Pb) free with 100% matte tin leadframe plating.

The IGBT driver also has internal gate resistors for minimum

2.3 to 5.5 V

VIN_VDRV

CHARGE

A8739 is a Xenon photoflash charger IC designed

TRIG

VBAT

V IN_VDRV

BAT

Control

IGBT Driver

Block

(B)

GND

DONE

(min) to support applications

Battery Input

2.0 to 5.5 V

VOUT Detect

sense

A8739

GATE

DONE

IGBT Gate

COUT

100F

315 V

VPULLUP

100 kΩ

Related parts for A8739EEETR-T

A8739EEETR-T Summary of contents

Page 1

Ultra-Small Mobile Adjustable Xenon Photoflash Features and Benefits ▪ Primary-side output voltage sensing; no resistor divider required ▪ Adjustable switch peak current limit up to 1.5 A with single-wire programming through the CHARGE pin ▪ Option to fine-tune target voltage ...

Page 2

... Ultra-Small Mobile Adjustable Xenon Photoflash A8739 Selection Guide Part Number Packing A8739EEETR-T 1500 pieces per reel Absolute Maximum Ratings Characteristic Symbol SW Pin V VIN_DRV, VBAT Pins CHARGE, TRIG, ¯ D ¯ ¯ O ¯ ¯ N ¯ ¯ E ¯ Pins Remaining Pins Operating Ambient Temperature ...

Page 3

Ultra-Small Mobile Adjustable Xenon Photoflash A8739 VBAT V – BAT ILIM Reference V ref DS VIN_DRV Decoder CHARGE TRIG Pin-out Diagram DONE 1 8 CHARGE TRIG 2 7 VIN_DRV PAD GATE 3 6 VBAT GND ...

Page 4

Ultra-Small Mobile Adjustable Xenon Photoflash A8739 ELECTRICAL CHARACTERISTICS guaranteed from −40°C to 85°C ambient, unless otherwise noted Characteristics VBAT Voltage Range VIN_DRV Voltage Range UVLO Enable Threshold UVLO Hysteresis V Supply Current IN VBAT Pin Supply Current Current Limit Primary-Side ...

Page 5

Ultra-Small Mobile Adjustable Xenon Photoflash A8739 ELECTRICAL CHARACTERISTICS specifications guaranteed from −40°C to 85°C ambient, unless otherwise noted Charge Pin Programming ILIM Programming High at CHARGE pin 2 ILIM Programming Low at CHARGE pin 2 Total ILIM Setup Time at ...

Page 6

Ultra-Small Mobile Adjustable Xenon Photoflash A8739 UVLO V IN CHARGE SW Target V V OUT DONE TRIG GATE Explanation of Events A: Start charging by pulling CHARGE to high, provided that V B: Charging stops when V C: Start a ...

Page 7

Ultra-Small Mobile Adjustable Xenon Photoflash A8739 IGBT drive waveforms are measured at pin, with capacitive load of 6800 pF Rising Signal Symbol Parameter Units/Division TRIGGER GATE ...

Page 8

Ultra-Small Mobile Adjustable Xenon Photoflash A8739 Charge Time versus Battery Voltage at Various ILIM Ω, Transformer L BAT 1.5 Efficiency versus Battery Voltage at Various ILIM ...

Page 9

Ultra-Small Mobile Adjustable Xenon Photoflash A8739 Final Output Voltage versus Battery Voltage at Various ILIM Ω, Transformer L BAT 328 327 326 325 324 323 322 321 320 1.5 2.0 Note: Output voltage is sensed from the ...

Page 10

Ultra-Small Mobile Adjustable Xenon Photoflash A8739 Average Input Current versus Battery Voltage at Various ILIM Ω, Transformer L BAT 0.7 0.6 0.5 0.4 0.3 0.2 0.1 0.0 1.5 Note: Peak switch current is limited by the maximum ...

Page 11

Ultra-Small Mobile Adjustable Xenon Photoflash A8739 Output Capacitor Charging at Various Peak Current Limits Test conditions 3 3 BAT Oscilloscope settings: Ch1 = ¯ D ¯ ¯ O ¯ ¯ N ¯ ...

Page 12

Ultra-Small Mobile Adjustable Xenon Photoflash A8739 Output Capacitor Charging at Various Battery Voltages Test conditions 3.0 V, ILIM3 (1.36 A Oscilloscope settings: Ch1 = ¯ D ¯ ¯ O ¯ ¯ N ¯ ¯ E ¯ ...

Page 13

Ultra-Small Mobile Adjustable Xenon Photoflash A8739 General Operation Overview The charging operation is started by a low-to-high signal on the CHARGE pin, provided that V is above the V IN strongly recommended to keep the CHARGE pin at logic low ...

Page 14

Ultra-Small Mobile Adjustable Xenon Photoflash A8739 As soon as a sufficient voltage has built up at the output capaci- tor, the IC enters Fast-Charging mode. In this mode, the next switching cycle starts after the secondary side current has stopped ...

Page 15

Ultra-Small Mobile Adjustable Xenon Photoflash A8739 ILIM Programming The peak current limit can be programmed to sixteen differ- ent levels, from 100% to 29%, with programming through the CHARGE pin. An internal digital circuit decodes the input clock signals, which ...

Page 16

Ultra-Small Mobile Adjustable Xenon Photoflash A8739 Output Voltage Adjustment The target output voltage of the A8739 is primarily determined by the transformer turns ratio 31.5 (V) × N OUT Typically N = 10, so the output voltage ...

Page 17

Ultra-Small Mobile Adjustable Xenon Photoflash A8739 Transformer Design 1. The transformer turns ratio, N, determines the output voltage 31.5 × N – OUT d where 31.5 is the typical value ...

Page 18

Ultra-Small Mobile Adjustable Xenon Photoflash A8739 Input Capacitor Selection Ceramic capacitors with X5R or X7R dielectrics are recom- mended for the input capacitor During initial Timer mode IN the device operates with 18 μs off-time. The resonant period ...

Page 19

Ultra-Small Mobile Adjustable Xenon Photoflash A8739 Layout Guidelines Key to a good layout for the photoflash capacitor charger circuit is to keep the parasitics minimized on the power switch loop (transformer primary side) and the rectifier loop (secondary side). Use ...

Page 20

Ultra-Small Mobile Adjustable Xenon Photoflash A8739 Recommended layout: C4 Schematic 0.1uF DONE CHARGE Top side Bottom side Top components Capacitor Charger with IGBT Driver VBAT C2 10uF R10 6 5 A8739 20k VBAT VIN_DRV GATE 1 2 ...

Page 21

Ultra-Small Mobile Adjustable Xenon Photoflash A8739 Package EE 8-Contact DFN/MLP with Exposed Thermal Pad D 9X 0.08 C 0.25 ±0.05 0.325 ±0.050 Copyright ©2009-2010, Allegro MicroSystems, Inc. The products described here are manufactured under one or more U.S. patents or ...

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