
FUNCTIONALITY GUIDE — SWITCHED MODE STEP-DOWN CONVERTERS
L1
PGND 1
SM2
L2
VIN_ SM1
VIN_ SM2
PGND 2
SM1
SYNCBUCK
P2
OUT
TPS65820
OperatingMode
OutputVoltage
PhaseControl
DischargeControl
OperatingMode
OutputVoltage
PhaseControl
DischargeControl
I2CREGISTERS
LSM 1
LSM 2
1.0-3.4V
600mA
0.6-1.8V
600mA
3.3 H
m
3.3 H
m
VO(SM2)
C20
10 F
m
C19
10 F
m
VO(SM1)
C22
10 F
m
C21
10 F
m
P1
STEP-DOWN SWITCHED MODE CONVERTERS: SM1 and SM2
www.ti.com .............................................................................................................................................................. SLVS663B – MAY 2006 – REVISED APRIL 2008
BUCK CONVERTERS, I2C PROGRAMMABLE OUTPUT VOLTAGE
Supply
PFM Mode
Standby
IO Max
PWM Freq
SLEW RATE, mV/
s, Set
Power Up Default
OUTPUT VOLTAGE (V), Set via I2C,
Mode
(mA)
and Phase
Separate Settings for Normal or
via I2C
Standby Mode
Range
# of Steps
Min
Acc
Range
# of
Min
Step
(%)
Steps
Step
SM1
PFM/PWM
Standby
0.6–1.8
32
40 mV
3
600
1.5MHz, 0
°
0, 0.24
8
0.24
ON, skip mode off,
with
mode
to 15.36
PWM only, 1.24
automatic
with
V(on/stby), 15.36
mode
distinct
mV/
s
selection or
voltage
PWM only.
available
.
SM2
Mode of
1–3.4
32
80mV
3
600
1.5MHz,
0,
8
0.48
ON, skip mode on,
Standby
operation set
0/90/180
0.48-
PWM/PFM, 1.8 V
mode set
270
°, with
30.72
(on/stby), 180
°,
via I2C
via I2C or
respect to
30.72 mV/
s
with
SM1, set via
GPIO pin
I2C
Figure 41. Required External Components, Recommended Values, External Connections
The TPS65820 has two highly efficient step down synchronous converters. The integration of the power stage
switching MOSFETs reduces the external component count, and only the external output inductor and filter
capacitor are required. The integrated power stage supports 100% duty cycle operation. Multiple operation
modes are available, enabling optimization of the overall system performance under distinct load conditions.
The converters have two modes of operation: a 1.5 MHz fixed frequency pulse width modulation (PWM) mode at
moderate to heavy loads, and a pulse frequency modulation (PFM) mode at light loads. The converter output
voltage is programmable via I2C registers SM1_SET1 and SM2_SET1.
When the SM1/SM2 converters are disabled an integrated switch automatically discharges the converter output
capacitor. The discharge switch function can be disabled by setting the control bits DISCHSM1 and DISCHSM2
to LO, in I2C registers SM1_SET2 and SM2_SET2.
Copyright 2006–2008, Texas Instruments Incorporated
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