LP87332B-Q1 Datasheet, PDF (16/73 Pages) Texas Instruments – Dual High-Current Buck Converter and Dual Linear Regulator

LP87332B-Q1
SNVSAT2 – JUNE 2017
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Feature Description (continued)
• Power Good signal (PGOOD) with selectable sources
• Average output current sensing (for PFM entry and load current measurement)
The following parameters can be programmed via registers, the default values are set by OTP bits:
• Output voltage
• Forced PWM operation
• Switch current limit
• Output voltage slew rate
• Enable and disable delays
There are two modes of operation for the buck converter, depending on the output current required: pulse-width
modulation (PWM) and pulse-frequency modulation (PFM). The converter operates in PWM mode at high load
currents of approximately 600 mA or higher. Lighter output current loads cause the converter to automatically
switch into PFM mode for reduced current consumption when forced PWM mode is disabled. The forced PWM
mode can be selected to maintain fixed switching frequency at all load current levels.
A block diagram of a single core is shown in Figure 6.
FB
RAMP
GENERATOR
-
ERROR
+^AMP
VOLTAGE
SETTING
SLEW RATE
VDAC
CONTROL
PROGRAMMABLE
PARAMETERS
SLAVE
INTERFACE
+ ^POWER
-
GOOD
CONTROL
BLOCK
LOOP
COMP
MASTER
INTERFACE
HS FET
CURRENT
SENSE
POS
CURRENT
LIMIT
GATE
CONTROL
NEG
CURRENT
LIMIT
LS FET
CURRENT
SENSE
ZERO
CROSS
DETECT
IADC
VIN
V_OUT
SW
GND
Copyright © 2016, Texas Instruments Incorporated
Figure 6. Detailed Block Diagram Showing One Core
7.3.1.2 Transition Between PWM and PFM Modes
PWM mode operation optimizes efficiency at mid to full load at the expense of light-load efficiency. The
LP87332B-Q1 converter operates in PWM mode at load current of about 600 mA or higher. At lighter load
current levels the device automatically switches into PFM mode for reduced current consumption when forced
PWM mode is disabled (AUTO mode operation). By combining the PFM and the PWM modes a high efficiency is
achieved over a wide output-load current range.
7.3.1.3 Buck Converter Load Current Measurement
Buck load current can be monitored via I²C registers. The monitored buck converter is selected with the
LOAD_CURRENT_BUCK_SELECT bit in SEL_I_LOAD register. A write to this selection register starts a current
measurement sequence. The regulator is automatically forced to PWM mode for the measurement period. The
measurement sequence is 50 µs long, maximum.
LP87332B-Q1 can be configured to give out an interrupt (I_MEAS_INT bit in INT_TOP_1 register) after the load
current measurement sequence is finished. Load current measurement interrupt can be masked with
I_MEAS_MASK bit (TOP_MASK_1 register). The measurement result can be read from registers I_LOAD_1 and
I_LOAD_2. Register I_LOAD_1 bits BUCK_LOAD_CURRENT[7:0] give out the LSB bits and register I_LOAD_2
bit BUCK_LOAD_CURRENT[8] the MSB bit. The measurement result BUCK_LOAD_CURRENT[8:0] LSB is 20
mA, and maximum code value of the measurement corresponds to 10.22 A.
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