Datasheet
VIN
EN
FB
TPS62120
PG
L 22 Hµ
SW
C
4.7 F
OUT
µ
V 1.8 V
100 A
OUT
µ
GND
R
1
R
2
SGND
VOUT
C
10
IN
Fµ
300 kW
240 kW
C
ff
R
pullup
PWR GOOD
100 kW
22 pF
DC
12 V
1 kW
High Impedance
Source
(
)
( )
1
2
OUT
REF
R
OUT REF
R
V
1 2
V
V = V 1 + with an internal reference voltage VREF typical 0.8 V
R = 1 R
´
- ´
z
1 ff
1
= = 25 kHz
2 R C
f
p´ ´ ´
1
1
C =
2 R 25 kHz
ff
p´ ´ ´
TPS62120
TPS62122
www.ti.com
SLVSAD5 –JULY 2010
Figure 38. TPS62120 1.8V VOUT Configuration Powered from a High-Impedance Source
OUTPUT VOLTAGE SETTING
The output voltage can be calculated to:
(5)
To minimize the current through the feedback divider network, R
2
should be within the range of 82kΩ to 360k.
The sum of R
1
and R
2
should not exceed ~1MΩ, to keep the network robust against noise. An external
feed-forward capacitor Cff is required for optimum regulation performance. R
1
and C
ff
places a zero in the
feedback loop.
(6)
The value for C
ff
can be calculated as:
(7)
Table 1 shows a selection of suggested values for the feedback divider network for most common output
voltages.
Table 1. Suggested Values for Feedback Divider Network
Voltage Setting [V] 3.06 3.29 2.00 1.80 1.20 5.00
R1 [kΩ] 510 560 360 300 180 430
R2 [kΩ] 180 180 240 240 360 82
Cff [pF] 15 22 22 22 27 15
OUTPUT FILTER DESIGN (INDUCTOR AND OUTPUT CAPACITOR)
The TPS6212X operates with effective inductance values in the range of 10µH to 33µH and with effective output
capacitance in the range of 1µF to 33µF. The device is optimized to operate for an output filter of L = 22µH and
C
OUT
= 4.7µF. Larger or smaller inductor/capacitor values can be used to optimize the performance of the device
for specific operation conditions. For more details, see the CHECKING LOOP STABILITY section.
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