Chip information, Layout procedure – Rainbow Electronics MAX8715 User Manual

Page 13

AMLCD Application

Figure 4 shows a power supply for active matrix (TFT-
LCD) flat-panel displays. Output-voltage transient per-
formance is a function of the load characteristic. Add or
remove output capacitance (and recalculate compen-
sation-network component values) as necessary to
meet transient performance. Regulation performance
for secondary outputs (V2 and V3) depends on the load
characteristics of all three outputs.

Layout Procedure

Good PC board layout and routing are required in high-
frequency switching power supplies to achieve good reg-

ulation, high efficiency, and stability. It is strongly recom-
mended that the evaluation kit PC board layouts be fol-
lowed as closely as possible. Place power components
as close together as possible, keeping their traces short,
direct, and wide. Avoid interconnecting the ground pins
of the power components using vias through an internal
ground plane. Instead, keep the power components
close together and route them in a star ground configura-
tion using component-side copper, then connect the star
ground to internal ground using multiple vias.

Chip Information

TRANSISTOR COUNT: 1012

MAX1790/MAX8715

Low-Noise Step-Up DC-DC Converters

______________________________________________________________________________________

Figure 4. Multiple-Output, Low-Profile (1.2mm max) TFT-LCD Power Supply

GND

18pF (MAX1790)
10pF (MAX8715)

27nF

C1, C2, C3, C4: TAIYO YUDEN LMK325BJ335MD (3.3

µF, 10V)

D1: ZETEX ZHCS1000 (20V, 1A, SCHOTTKY) OR MOTOROLA MBRM120ET3
D2, D3, D4: ZETEX BAT54S (30V, 200mA, SCHOTTKY)
L1: SUMIDA CLQ4D10-6R8 (6.8

µH, 0.8A) OR SUMITOMO CXLM120-6R8

274k

Ω

44.2k

Ω

FREQ

3.0V TO 3.6V

+26V

5mA

V1
9V
150mA

V3
-9V
10mA

COMP

SHDN

0.47

µF

0.1

µF

0.1

µF

MAX1790
MAX8715

470pF (MAX1790)
750pF (MAX8715)

150k

Ω (MAX1790)

82k

Ω (MAX8715)

3.3

µF