Texas Instruments TPS65820 Evaluation Module TPS65820EVM TPS65820EVM Datenbogen
Produktcode
TPS65820EVM
INPUT CAPACITOR SELECTION, SM1, SM2 CONVERTERS
OUTPUT VOLTAGE SELECTION, SM1, SM2 CONVERTERS
R1
+
ƪ
V
SMxOUT
V
FB
*
1
ƫ
R2
(16)
DESIGN EXAMPLES
SM1, SM2 CONVERTER DESIGN EXAMPLE
L
target
+
V
OUT
0.3
I
OUT_MAX
ƪ
1
*
V
OUT
V
IN_MAX
ƫ
fsw
+
3.35
m
H, 3.3
m
H is a good target.
(17)
C
+
1
L[2
p
fc]
2
+
10.5
m
F 10
m
F is a good target.
(18)
CHARGER DESIGN EXAMPLE
R
ISET
+
K
SET
V
SET
I
PGM
+
1 k
W
(19)
R
DPPM
+
V
DPPM_OUT
K
DPPM
I
DPPM
+
3.74 k
W
(20)
SLVS663B – MAY 2006 – REVISED APRIL 2008
..............................................................................................................................................................
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Buck converters have a pulsating input current that can generate high input voltage spikes at V
IN
. A low ESR
input capacitor is required to filter the input voltage, minimizing the interference with other circuits connected to
the same power supply rail. Each dc-dc converter requires a 10-
the same power supply rail. Each dc-dc converter requires a 10-
µ
F ceramic input capacitor on its input pin.
Typically the output voltage is programmed by the I
2
C. An external divider can be added to raise the output
voltage, if the available I
2
C values do not meet the application requirements. Care must be taken with this special
option, since this external divider (gain factor) would apply to any selected I
2
C output voltage value for this
converter.
calculates R1, Let R2 = 20 k
Ω:
Where V
FB
is the I
2
C selected voltage, is the desired output voltage and R1/R2 is the feedback divider.
Design Conditions and Parametrs for SM1 or SM2:
Vin_SM1/2: 4.6V typical (May be less if input source is limited).
Vout_SM1/2: 1.24 V
Iout_max: 0.6 A
fsw = 1500 kHz
fc = 25 kHz
Vout_SM1/2: 1.24 V
Iout_max: 0.6 A
fsw = 1500 kHz
fc = 25 kHz
Design Conditions and Parameters for Charger:
Vout: 4.6 V; (OUT pin is input to charger)
Fast-charge current, I
Fast-charge current, I
PGM
: 1 A
DPPM-OUT threshold: 4.3 V; (charging current reduces when OUT falls to this level)
Safety timer: 5 hr
Battery short-circuit delay, t
Safety timer: 5 hr
Battery short-circuit delay, t
DELAY
: 47
µ
s; (delays BAT short circuit during hot plug of battery)
TS Temperature range: Disabled
K
K
SET
= 400; V
SET
= 2.5 V; K
DPPM
= 1.15; I
DPPM
= 100
µ
A; K
TMR
= 0.36 s/
Ω
Program Fast Charge Current Level:
Program DPPM_OUT Voltage Level (Level at Which Charging Current Reduces)
90
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