LM3488MMX/NOPB National Semiconductor, LM3488MMX/NOPB Datasheet - Page 10
![IC CTRLR SWITCH REG N-CH 8-MSOP](/photos/6/57/65756/pkg_mua08a_sml.jpg)
LM3488MMX/NOPB
Manufacturer Part Number
LM3488MMX/NOPB
Description
IC CTRLR SWITCH REG N-CH 8-MSOP
Manufacturer
National Semiconductor
Type
Step-Up (Boost), Flyback, Sepicr
Datasheet
1.LM3488MMNOPB.pdf
(24 pages)
Specifications of LM3488MMX/NOPB
Internal Switch(s)
No
Synchronous Rectifier
No
Number Of Outputs
1
Voltage - Output
Adj to 1.26V
Current - Output
1A
Frequency - Switching
100kHz ~ 1MHz
Voltage - Input
2.97 ~ 40 V
Operating Temperature
-40°C ~ 125°C
Mounting Type
Surface Mount
Package / Case
8-MSOP, Micro8™, 8-uMAX, 8-uSOP,
Lead Free Status / RoHS Status
Lead free / RoHS Compliant
Power - Output
-
Other names
*LM3488MMX
*LM3488MMX/NOPB
LM3488MMX
*LM3488MMX/NOPB
LM3488MMX
Available stocks
Company
Part Number
Manufacturer
Quantity
Price
Company:
Part Number:
LM3488MMX/NOPB
Manufacturer:
ATMEL
Quantity:
3 410
www.national.com
SLOPE COMPENSATION RAMP
The LM3488 uses a current mode control scheme. The main
advantages of current mode control are inherent cycle-by-cy-
cle current limit for the switch, and simpler control loop char-
acteristics. It is also easy to parallel power stages using
current mode control since as current sharing is automatic.
Current mode control has an inherent instability for duty cy-
cles greater than 50%, as shown in
small increase in the load current causes the switch current
to increase by ΔI
O
. The effect of this load change, ΔI
FIGURE 1. Basic Operation of the PWM comparator
Figure
FIGURE 2. Sub-Harmonic Oscillation for D>0.5
2. In
Figure
1
, is :
2, a
10
From the above equation, when D > 0.5, ΔI
than ΔI
very small perturbation in the load will cause the disturbance
to increase.
To prevent the sub-harmonic oscillations, a compensation
ramp is added to the control signal, as shown in
With the compensation ramp,
O
. In other words, the disturbance is divergent. So a
1
10138809
will be greater
Figure
10138807
3.