MIC23060-G4YMT TR Micrel Inc, MIC23060-G4YMT TR Datasheet - Page 11

• Manufacturer Part Number: MIC23060-G4YMT TR
• Description: IC POWER MGMT SEQUENCE 12TMLF
• Manufacturer: Micrel Inc

Specifications of MIC23060-G4YMT TR

• Applications: Power Supply Sequencer
• Voltage - Supply: 2.7 V ~ 5.5 V
• Current - Supply: 43µA
• Operating Temperature: -40°C ~ 125°C
• Mounting Type: Surface Mount
• Package / Case: 12-TMLF®
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Other names: 576-3650-2; MIC23060-G4YMT TR

modes, S2 controls the LDO sequence and S1 controls
the DC/DC sequence. Here is a Truth Table followed by
a flow chart of the sequencing events:
Flow Chart of the Enable & Disable sequence
DLY
The value of capacitor on this pin is used to program the
enable and disable delay times. The delay time follows
the following equation:
Where nominally: V
Micrel, Inc.
April 2010
S3
X
X
0
0
1
1
∴ T
T
DLY
EN
EN
S2
0
0
0
1
DLY
= V
(ms) = C
DLY
DLY
EN
EN
S1
.C
0
0
0
1
= 1.25V, I
DLY
DLY
/ I
(nF)
Sequence
ALL OFF
DC-DC ON 1
LDO ON 1
DC-DC ON 1
LDO ON 1
ALL ON
DLY
DLY
= 1.25μA
st
st
/ OFF 1
/ OFF 2
st
st
/ OFF 1
/ OFF 2
st
nd
st
nd
11
For example, an application where the LDO should be
enabled 50ms before the DC/DC and disabled 50ms
after the DC-DC, the pins should be set as follows:
S1 = 0
S3 = 1
C
S2 = Enable stimulus
Duty Cycle
The typical maximum duty cycle of the MIC23060 is
80%.
Efficiency Considerations
Efficiency is defined as the amount of useful output
power, divided by the amount of power supplied.
Maintaining high efficiency serves two purposes. It
reduces power dissipation in the power supply,
simplifying thermal design considerations, and it reduces
current consumption for battery powered applications.
Reduced current draw from a battery increases the
devices operating time and is critical in hand held
devices.
There are two types of losses in switching converters;
DC losses and switching losses. DC losses are simply
the power dissipation of I
high side switch during the on cycle. Power loss is equal
to the high side MOSFET R
Current squared. During the off cycle, the low side N-
channel MOSFET conducts, also dissipating power.
Device operating current also reduces efficiency. The
product of the quiescent (operating) current and the
supply voltage represents another DC loss. The current
required driving the gates on and off at a constant 4MHz
frequency and the switching transitions make up the
switching losses.
DLY
= 50nF
Efficiency
Detail of the delay timer circuit.
(%)
=
⎛
⎜ ⎜
⎝
V
2
OUT
R. Power is dissipated in the
V
DSON
IN
×
×
I
I
multiplied by the Switch
IN
OUT
⎞
⎟ ⎟
⎠
×
M9999-042210-B
100
MIC23060