A8740EEETR-T Allegro Microsystems Inc, A8740EEETR-T Datasheet - Page 14

• Manufacturer Part Number: A8740EEETR-T
• Description: Photoflash Capacitor Charger
• Manufacturer: Allegro Microsystems Inc
• Series: -r

Specifications of A8740EEETR-T

• Constant Current: -
• Constant Voltage: -
• Topology: Flyback
• Number Of Outputs: 1
• Internal Driver: No
• Type - Primary: Flash/Torch
• Type - Secondary: -
• Frequency: -
• Voltage - Supply: 1.5 V ~ 5.5 V
• Voltage - Output: -
• Mounting Type: *
• Package / Case: *
• Operating Temperature: -40°C ~ 85°C
• Lead Free Status / Rohs Status: Lead free / RoHS Compliant

A8740
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 short, thick traces for connections to the transformer primary
and SW pin. It is important that the ¯ D ¯ ¯ ¯ O ¯ ¯¯ N ¯ ¯ E ¯ signal trace and other
signal traces be routed away from the transformer and other
switching traces, in order to minimize noise pickup. In addition,
high voltage isolation rules must be followed carefully to avoid
Recommended Components
C1, Input Capacitor
C2
COUT, Photoflash
Capacitor
D1, Output Diode
T1, Transformer
Component
10 μF, ±10%, 6.3 V, X5R ceramic
capacitor (0805)
0.1 μF, 6.3 V X5R ceramic capacitor
100 μF / 330 V
2 x 250 V, 225 mA, 5 pF
L
6.5 × 8 × 4 mm
L
5.6 × 5.6 × 3 mm
PRIMARY
PRIMARY
= 12.8 μH, N= 10.25,
= 6 μH, N= 10.4,
Rating
Ultra Small Mobile Phone Xenon Photoflash
Capacitor Charger with IGBT Driver
breakdown failure of the circuit board.
Avoid placing any ground plane area underneath the transformer
secondary and diode, to minimize parasitic capacitance.
Connect the EE package PAD to the ground pad for better ther-
mal performance. Use ground planes on the top and bottom layers
below the IC and connect them through multiple thermal vias.
Refer to the figures on page 18 for recommended layout.
JMK212BJ106K
EPH-31ELL101B131S Chemi-Con
BAV23S
T-16-024A
LDT565630T-001
Part Number
115 Northeast Cutoff
1.508.853.5000; www.allegromicro.com
Allegro MicroSystems, Inc.
Worcester, Massachusetts 01615-0036 U.S.A.
Taiyo Yuden
Philips Semiconductor,
Fairchild Semiconductor
Tokyo Coil Electric
TDK
Source
14