MAX1620EEE+ Maxim Integrated Products, MAX1620EEE+ Datasheet - Page 17

• Manufacturer Part Number: MAX1620EEE+
• Description: IC LCD BIAS SUPP DGTL ADJ 16QSOP
• Manufacturer: Maxim Integrated Products

Specifications of MAX1620EEE+

• Applications: LCD Display
• Current - Supply: 150µA
• Voltage - Supply: 3 V ~ 5.5 V
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 16-QSOP
• Output Current: 0.07 A
• Input Voltage: 1.8 V to 20 V
• Switching Frequency: 300 KHz
• Maximum Operating Temperature: + 85 C
• Mounting Style: SMD/SMT
• Minimum Operating Temperature: - 40 C
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

LCDON typically drives an external PNP transistor,
switching a positive V
current in the PNP; R6 turns off the PNP when LCDON is
floating. R6 and R7 can be the same value. Choose R7
such that the minimum base current is greater than 1/50
of the collector current. For example, assume V
= 12.5V and I
Remember that LCD voltage is the regulated output volt-
age minus the drop across the PNP switch. The drop
across the external transistor (typically 300mV) must be
accounted for.
If a PFET is preferred for the LCDON switch, R6 and R7
in Figure 4 may both be raised to 1MΩ or more to reduce
operating current. Be sure to choose a P
quate breakdown voltage. Since load current is typically
on the order of 10mA, an on-resistance of 10Ω or less is
usually adequate.
Practical inductor values range from 33µH to 1mH;
however, 100µH is a good choice for a wide range of
applications. Inductors with a ferrite core or equivalent
are recommended. The inductor’s current rating should
exceed the peak current as set by the k-factor and the
Table 5. Maximum Inductance vs. I
Table 6. Inductor List
Sumida
USA [phone]
Japan 81-3-3607-5111
Coilcraft
[phone]
TDK
[phone]
IOUT
COMPANY
R7 ≤ 50 x (12.5 - 0.7) / 10mA = 59kΩ
10mA
20mA
30mA
5mA
LCD
= 10mA, then determine R7 as follows:
______________________________________________________________________________________
OUT
Digitally Adjustable LCD Bias Supplies
100µH
56µH
27µH
18µH
1.8V
to the LCD. R7 limits the base
CD43
CD54
CDRH62B
DO1608
DT1608
NLC565050
TPF0410
Choosing an Inductor
PART
150µH
82µH
39µH
27µH
2.7V
FET
µH RANGE
OUT
Up to 68µH
Up to 220µH
Up to 330µH
Up to 1mH
Up to 400µH
Up to 1mH
Up to 1mH
with ade-
OUT,MIN
and V
220µH
100µH
56µH
33µH
3.6V
BATT,MIN
coil inductance; however, for most inductor types, the
coil’s specified current can be exceeded by 20% with
no impact on efficiency.
The peak current is set by the coil inductance as follows:
and
If we assume that V
25V, I
16µs-V, then the required I
and
The next-lowest practical inductor value is 100µH. Its
current rating must be:
Table 5 summarizes the minimum inductance value
needed to provide various output currents at several
minimum input voltages. Table 6 lists some suitable coil
types and manufacturers, but is not intended to be a
complete list.
V
BATT,MIN
I
24µs-V (maximum k-factor) / 100µH = 240mA
OUT,MIN
OUT,MIN
SIZE IN mm (H x W x L)
3.2 x 4 diameter
4.5 x 5.2 diameter
3 x 6.2 x 6.2
3.18 x 4.45 x 6.6
3.18 x 4.45 x 6.6
5 x 5 x 5.6
4 diameter x 10 L
I
PK
(20V output)
330µH
150µH
82µH
56µH
L ≤ = 16µs-V / 142mA = 113µH
5.4V
= 2 x 15mA x 25 / 5.3 = 142mA
= 15mA, and a minimum k-factor of
1
2
I
PK
BATT,MIN
I
PK
= k-factor / L
PK
390µH
220µH
100µH
68µH
is:
7.2V
V
BATT,MIN
= 5.3V, V
/ V
COMMENTS
Leaded coil
Shielded
Shielded
OUT,MAX
OUT,MAX
680µH
330µH
180µH
120µH
12V
17
=