AOZ1037PI Alpha & Omega Semiconductor Inc, AOZ1037PI Datasheet - Page 8

• Manufacturer Part Number: AOZ1037PI
• Description: IC BUCK SYNC ADJ 5A SO8
• Manufacturer: Alpha & Omega Semiconductor Inc
• Series: EZBuck™r
• Type: Step-Down (Buck), PWM - Current Moder

Specifications of AOZ1037PI

• Featured Product: The AOZ103x Family Synchronous Buck Regulator
• Internal Switch(s): Yes
• Synchronous Rectifier: Yes
• Number Of Outputs: 1
• Voltage - Output: 0.8 V ~ 18 V
• Current - Output: 5A
• Frequency - Switching: 500kHz
• Voltage - Input: 4.5 V ~ 18 V
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 8-SOIC (0.154", 3.90mm Width) Exposed Pad
• Lead Free Status / Rohs Status: Lead free / RoHS Compliant
• Other names: 785-1256-2

Some standard value of R1, R2 and most used output
voltage values are listed in Table 1.
Table 1.
The combination of R
avoid drawing excessive current from the output, which
will cause power loss.
Protection Features
The AOZ1037 has multiple protection features to prevent
system circuit damage under abnormal conditions.
Over Current Protection (OCP)
The sensed inductor current signal is also used for over
current protection. Since the AOZ1037 employs peak
current mode control, the COMP pin voltage is
proportional to the peak inductor current. The COMP pin
voltage is limited to be between 0.4V and 2.5V internally.
The peak inductor current is automatically limited cycle
by cycle.
When the output is shorted to ground under fault
conditions, the inductor current decays very slow during
a switching cycle because of V
catastrophic failure, a secondary current limit is designed
inside the AOZ1037. The measured inductor current is
compared against a preset voltage which represents the
current limit. When the output current is more than
current limit, the high side switch will be turned off and
EN pin will be pulled down. The converter will initiate a
soft start once the over-current condition disappears.
Power-On Reset (POR)
A power-on reset circuit monitors the input voltage. When
the input voltage exceeds 4.1V, the converter starts
operation. When input voltage falls below 3.7V, the
converter will be shut down.
Rev. 1.1 September 2010
V
O
0.8
1.2
1.5
1.8
2.5
3.3
5.0
(V)
1
and R
R
1
12.7
4.99
21.5
31.1
52.3
1.0
10
(k
2
Ω
should be large enough to
O
)
= 0V. To prevent
R
Open
2
11.5
10.2
10
10
10
10
(k
Ω
www.aosmd.com
)
Thermal Protection
An internal temperature sensor monitors the junction
temperature. It shuts down the internal control circuit and
high side PMOS if the junction temperature exceeds
150°C. The regulator will restart automatically under the
control of soft-start circuit when the junction temperature
decreases to 100°C.
Application Information
The basic AOZ1037 application circuit is show in
Figure 1. Component selection is explained below.
Input Capacitor
The input capacitor must be connected to the V
PGND pin of AOZ1037 to maintain steady input voltage
and filter out the pulsing input current. The voltage rating
of input capacitor must be greater than maximum input
voltage plus ripple voltage.
The input ripple voltage can be approximated by
equation below:
Since the input current is discontinuous in a buck
converter, the current stress on the input capacitor is
another concern when selecting the capacitor. For a buck
circuit, the RMS value of input capacitor current can be
calculated by:
if we let m equal the conversion ratio:
The relationship between the input capacitor RMS
current and voltage conversion ratio is calculated and
shown in Figure 2 below. It can be seen that when V
half of V
worst current stress on C
-------- -
V
V
I
ΔV
CIN_RMS
IN
O
IN
=
IN
=
m
, C
---------------- -
f
×
=
IN
I
O
C
I
is under the worst current stress. The
O
IN
×
×
⎛
⎜
⎝
-------- - 1
V
1
V
IN
–
O
IN
-------- -
V
⎛
⎜
⎝
V
is 0.5 x I
IN
O
–
⎞
⎟
⎠
-------- -
V
V
×
IN
O
-------- -
V
V
⎞
⎟
⎠
IN
O
O
.
AOZ1037
Page 8 of 14
IN
pin and
O
is