MAX8667ETEHR+ Maxim Integrated Products, MAX8667ETEHR+ Datasheet - Page 14

• Manufacturer Part Number: MAX8667ETEHR+
• Description: IC DC-DC CONV W/DUAL LDO 16TQFN
• Manufacturer: Maxim Integrated Products
• Type: Step-Down (Buck)r

Specifications of MAX8667ETEHR+

• Internal Switch(s): Yes
• Synchronous Rectifier: Yes
• Number Of Outputs: 4
• Voltage - Output: 1.2V, 1.8V, 2.6V, 2.8V
• Current - Output: 600mA, 1.2A
• Frequency - Switching: 1.5MHz
• Voltage - Input: 2.6 ~ 5.5 V
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 16-TQFN Exposed Pad
• Power - Output: 1.67W
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

1.5MHz Dual Step-Down DC-DC Converters
with Dual LDOs and Individual Enables
for peak ripple current and load transients. The step-
down converter’s unique architecture has minimal cur-
rent overshoot during startup and load transients and in
most cases, an inductor capable of 1.3x the maximum
load current is acceptable.
For output voltages above 2V, when light-load efficiency
is important, the minimum recommended inductor is
2.2µH. For optimum voltage-positioning load transients,
choose an inductor with DC series resistance in the
50mΩ to 150mΩ range. For higher efficiency at heavy
loads (above 200mA) and minimal load regulation,
keep the inductor resistance as small as possible. For
light-load applications (up to 200mA), higher resistance
is acceptable with very little impact on performance.
The input capacitor for the step-down converters (C2 in
Figures 3 and 4) reduces the current peaks drawn from
the battery or input power source and reduces switch-
ing noise in the IC. The impedance of C2 at the switch-
ing frequency should be very low. Surface-mount
ceramic capacitors are a good choice due to their
small size and low ESR. Make sure the capacitor main-
tains its capacitance over temperature and DC bias.
Ceramic capacitors with X5R or X7R temperature char-
acteristics generally perform well. A 10µF ceramic
capacitor is recommended.
A 4.7µF ceramic capacitor is recommended for the
LDO input capacitor (C3 in Figure 3).
The step-down output capacitors (C6 and C7 in Figures
3 and 4) are required to keep the output-voltage ripple
Table 1. Recommended Inductors
14
MANUFACTURER
FDK
FDK
Murata
Sumida
TDK
TOKO
TOKO
Wurth
Taiyo Yuden
______________________________________________________________________________________
Step-Down Output Capacitors
LQH32CN2R2M5
MDT2520-CR
GLF251812T
INDUCTOR
MIPF2520D
CDRH2D09
TPC Series
TPC Series
MIPF2016
CB2518T
LQM31P
D2812C
Capacitor Selection
Input Capacitors
L (µH)
2.2
2.2
2.2
2.2
2.2
2.2
2.2
2.2
2.2
4.7
2.2
R
small and to ensure regulation loop stability. These
capacitors must have low impedance at the switching
frequency. Surface-mount ceramic capacitors are a
good choice due to their small size and low ESR. Make
sure the capacitor maintains its capacitance over tem-
perature and DC bias. Ceramic capacitors with X5R or
X7R temperature characteristics generally perform well.
The output capacitance can be very low. For most appli-
cations, a 2.2µF ceramic capacitor is sufficient. For C7 of
the MAX8668, a 2.2µF (V
> 1.8V) ceramic capacitor is recommended. For opti-
mum load-transient performance and very low output rip-
ple, the output capacitor value in µF should be equal to
or greater than the inductor value in µH.
The feed-forward capacitors on the MAX8668 (C4 and
C5 in Figure 4) set the feedback loop response, control
the switching frequency, and are critical in obtaining
the best efficiency possible. Small X7R and C0G
ceramic capacitors are recommended.
For OUT1, calculate the value of C4 as follows:
For OUT2, calculate the value of C5 and C10 as fol-
lows:
Rearranging the formulas:
L
110
220
120
200
140
124
80
97
80
55
90
(mΩ)
(C10 / C5) + 1 = (V
CURRENT RATING (A)
C10 = 2 x C
C4 = 1.2 x 10
C
C
C5 = C
ff
ff
= 1.2 x 10
= C5 + (C10 / 2)
0.79
0.44
0.77
1.35
0.51
1.1
1.3
0.9
0.6
0.7
1.8
ff
OUT
– (C10 / 2)
ff
OUT2
/ V
x (V
-5
-5
FB
(s/V) x (V
(s/V) x (V
Feed-Forward Capacitor
OUT
≤ 1.8V) or a 4.7µF (V
), where V
- V
FB
OUT
OUT
L x W x H (mm)
3.2 x 2.5 x 1.55
3.2 x 1.6 x 0.95
2.5 x 1.8 x 1.35
2.0 x 1.6 x 1.0
2.5 x 2.0 x 1.0
3.2 x 3.2 x 1.0
2.8 x 2.8 x 1.2
2.5 x 2.0 x 1.0
4.0 x 4.0 x 1.1
4.0 x 4.0 x 1.1
2.5 x 1.8 x 2.0
)/(V
FB
/ R3)
/ R1)
OUT
is 0.6V.
+ V
OUT2
FB
)