Datasheet

R2 +
b ) a V
SH
a I
LIM
R1 +
b ) a V
SH
(
1 * a
)
I
LIM
b + DCR A
C
I
PEAK
)
ǒ
V
RAMP
2 Nph
Ǔ
a +
V
RAMP
V
IN
ILIMx
VSHARE
TPS40140
R1
V
OUT
R2
UDG-12123
TPS40140
www.ti.com SLUS660H –SEPTEMBER 2005–REVISED JUNE 2013
Figure 5-10. Selecting Overcurrent Threshold Resistors, R2 and R1
The two factors, alpha and beta help simplify the final equations and are given by Equation 13 and
Equation 14.
(13)
(14)
R1 is shown in Equation 15.
(15)
R2 is shown in Equation 16.
(16)
where
• V
RAMP
is the ramp amplitude (0.5 V typ)
• V
IN
is the input voltage
• DCR is the inductor equivalent DC resistance
• A
C
is the gain transfer to comparator
• I
OC
is the single-phase DC overcurrent trip point
• I
PEAK
is the peak single-phase inductor current
• N
ph
is 6 if PHSEL voltage = 1.6 V ±0.2 V, otherwise N
ph
= 8
• V
SHR
is the V
SHARE
reference voltage (typ 1.8 V)
• I
LIM
is the current limit, output current (typ 20 μA)
• Range of variable is specified in the Section 2.4 ELECTRICAL CHRACTERISTICS table.
Copyright © 2005–2013, Texas Instruments Incorporated APPLICATION INFORMATION 27
Submit Documentation Feedback
Product Folder Links: TPS40140