MAX1692EUB+ Maxim Integrated Products, MAX1692EUB+ Datasheet - Page 9

• Manufacturer Part Number: MAX1692EUB+
• Description: IC REG PWM STEP-DN 5.5VIN 10UMAX
• Manufacturer: Maxim Integrated Products
• Type: Step-Down (Buck)r

Specifications of MAX1692EUB+

• Internal Switch(s): Yes
• Synchronous Rectifier: Yes
• Number Of Outputs: 1
• Voltage - Output: 1.25 ~ 5.5 V
• Current - Output: 600mA
• Frequency - Switching: 750kHz
• Voltage - Input: 2.7 ~ 5.5 V
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 10-MSOP, Micro10™, 10-uMAX, 10-uSOP
• Power - Output: 444mW
• Output Voltage: 1.25 V to 5.5 V
• Input Voltage: 2.7 V to 5.5 V
• Supply Current: 85 uA
• Maximum Operating Temperature: + 85 C
• Minimum Operating Temperature: - 40 C
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

Choose input- and output-filter capacitors to service
inductor currents with acceptable voltage ripple. The
input-filter capacitor also reduces peak currents and
noise at the voltage source. In addition, connect a low-
ESR bulk capacitor (>10µF suggested) to the input.
Select this bulk capacitor to meet the input ripple
requirements and voltage rating, rather than capacitor
size. Use the following equation to calculate the maxi-
mum RMS input current:
When selecting an output capacitor, consider the out-
put-ripple voltage and approximate it as the product of
the ripple current and the ESR of the output capacitor.
where ESR
output capacitor.
The MAX1692’s loop gain is relatively low, enabling the
use of small, low-value output filter capacitors. Higher
values provide improved output ripple and transient
response. Lower oscillator frequencies require a larger-
value output capacitor. When PWM/PFM is used, verify
capacitor selection with light loads during PFM opera-
tion, since output ripple is higher under these condi-
tions. Low-ESR capacitors are recommended.
Capacitor ESR is a major contributor to output ripple
(usually more than 60%). Ordinary aluminum-electrolyt-
ic capacitors have high ESR and should be avoided.
Low-ESR aluminum-electrolytic capacitors are accept-
able and relatively inexpensive. Low-ESR tantalum
capacitors are better and provide a compact solution
for space-constrained surface-mount designs. Do not
exceed the ripple-current ratings of tantalum capaci-
tors. Ceramic capacitors have the lowest ESR overall,
and OS-CON
high-value electrolytic types.
It is generally not necessary to use ceramic or OS-CON
capacitors for the MAX1692; consider them only in very
compact, high-reliability, or wide-temperature applica-
tions where the expense is justified. When using very-
low-ESR capacitors, such as ceramic or OS-CON,
check for stability while examining load-transient
response. The output capacitor is determined by ensur-
ing that the minimum capacitance value and maximum
OS-CON is a trademark of Sanyo Corp.
I
RMS
V
C2
RIPPLE
= I
™
is the equivalent-series resistance of the
OUT
capacitors have the lowest ESR of the
_______________________________________________________________________________________
=
[V
OUT
[V
[2 · f
OUT
(V
OSC
IN
(V
Capacitor Selection
(L) (V
IN
- V
- V
OUT
IN
OUT
)]
)] · ESR
1/2
)] /
· V
IN
C2
PWM Step-Down Regulator
ESR values are met:
where C2 is the output filter capacitor, V
nal reference voltage of 1.25V, V
input voltage (2.7V), R
tance of 0.1 , and f
quency (typically 750kHz). These equations provide the
minimum requirements. The value of C2 may need to
be increased for operation at duty-cycle extremes.
Tables 1 and 2 provide recommended inductor and
capacitor sizes at various external sync frequencies.
Table 3 lists suppliers for the various components used
with the MAX1692.
Figures 2 and 3 are standard application circuits opti-
mized for power and board space respectively. The cir-
cuit of Figure 2 is the most general of the two, and
generates 1.8V at 600mA.
The circuit of Figure 3 is optimized for smallest overall
size. Cellular phones are using low voltage for base-
band logic and have critical area and height restric-
tions. This circuit operates from a single Li-ion battery
(2.9V to 4.5V) and delivers up to 200mA at 1.8V. It uses
small ceramic capacitors at the input and output and a
tiny chip inductor such as the NLC322522T series from
TDK. With the MAX1692 in a 10-pin µMAX package, the
entire circuit can fit in only 60mm
2.4mm height.
Figure 3. Miniaturized 200mA Output Circuit Fits in 60mm
Low-Noise, 5.5V-Input,
4.7 F
C2 > 2V
+2.9V TO +4.5V
C5
ON
0.1 F
V
/
IN
C4
OFF
Standard Application Circuits
REF
R
(1 + V
SYNC/
ESR
IN
BP
SHDN
REF
LIM
PWM
MAX1692
< (R
OUT
GND
OSC
/V
SENSE
SENSE
IN(MIN)
PGND
LX
FB
is the internal oscillator fre-
)(V
is the internal sense resis-
) / (V
OUT
10 H
IN
C5
47pF
L1
2
(min) is the minimum
OUT
) / (V
and have less than
V
R1
138k
R2
301k
OUT
· R
REF
REF
= 1.8V @ 200mA
SENSE
)
10 F
is the inter-
C2
· f
2
OSC
10 F
9
)