LTC3440EMS Linear Technology, LTC3440EMS Datasheet - Page 10

• Manufacturer Part Number: LTC3440EMS
• Description: IC DC/DC CONV BUCK-BOOST 10-MSOP
• Manufacturer: Linear Technology
• Type: Step-Down (Buck), Step-Up (Boost)r

Specifications of LTC3440EMS

• Internal Switch(s): Yes
• Synchronous Rectifier: Yes
• Number Of Outputs: 1
• Voltage - Output: 2.5 ~ 5.5 V
• Current - Output: 600mA
• Frequency - Switching: 2MHz
• Voltage - Input: 2.5 ~ 5.5 V
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 10-MSOP, Micro10™, 10-uMAX, 10-uSOP
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant
• Power - Output: -

OPERATIO
LTC3440
voltage from the error amp to determine the control mode,
therefore full-time 4-switch mode is required to maintain
the Buck/Boost function. The efficiency below 1mA
becomes dominated primarily by the quiescent current
and not the peak efficiency. The equation is given by:
where (ηbm) is typically 79% during Burst Mode opera-
tion for an ESR of the inductor of 50mΩ. For 200mΩ of
inductor ESR, the peak efficiency (ηbm) drops to 75%.
10
Efficiency Burst
U
≈
( bm) • I
25 A I
η
μ +
A
B
A
B
Figure 4. Inductor Discharge Cycle During Burst Mode Operation
V
Figure 3. Inductor Charge Cycle During Burst Mode Operation
V
7
LOAD
IN
7
LOAD
IN
SW1
SW1
3
3
+
–
dT
dI
dT
dI
≈ –
GND
GND
≈
L
L
5
5
V
V
L
IN
OUT
L
–
+
SW2
SW2
4
4
D
V
C
D
C
V
OUT
6
OUT
6
400mA
400mA
0mA
0mA
Burst Mode Operation to Fixed Frequency Transient
Response
When transitioning from Burst Mode operation to fixed
frequency, the system exhibits a transient since the modes
of operation have changed. For most systems this tran-
sient is acceptable, but the application may have stringent
input current and/or output voltage requirements that
dictate a broad-band voltage loop to minimize the tran-
sient. Lowering the DC gain of the loop will facilitate the
task (10M FB to V
Type 3 compensation is also recommended to broad band
the loop and roll off past the two pole response of the LC
of the converter (see Closing the Feedback Loop).
T1
T2
C
) at the expense of DC load regulation.
3440 F03
3440 F04
3440fb