High Impedance Mode

Output Inductor and Capacitance Selection Guidelines

OUT

OUT

1

=

o

2

L

C

f

p

´

´

(1)

Pre-Regulator Application

State Machine Table and State Diagram

bq24152

When control bit of HZ-MODE is set to "1" and the OTG pin is not in active status, the bq24152 operates in high

impedance mode, with the impedance in VBUS pin higher than 165 k

Ω. In high impedance mode, a crude

not. If the crude 32 second timer expires, the bq24152 operates in 32 minute mode and the crude 32 second

timer is disabled. In 32 minute mode, when VBUS is below UVLO, the bq24152 operates in high impedance

mode regardless of the setting of the HZ_MODE bit.

The bq24152 provides internal loop compensation. With this scheme, the best stability occurs when the LC

To reduce the output voltage ripple, a ceramic capacitor with the capacitance between 4.7

µF and 47 µF is

Figure 2 shows a typical pre-regulator application that the bq24152 operates as a DC/DC converter, with the

termination disabled. The robust internal compensation design ensures the stable operation when the

host-controlled switch is turned off. With the input overvoltage protection, output current regulation and high

efficiency power conversion, the bq24152 is an ideal choice for pre-regulator used in pulse charging applications.

Based on the previously-described operation modes, the definitions of all operation states are shown in Table 3

and Table 4, whereas the relationship among different states is shown in Figure 26.

Table 3. State Machine Table 1 of bq24152

MODE

POWER DOWN

CHARGE CONFIGURE

SHORT CIRCUIT

PWM CHARGE

OPA_MODE = 0

OPA_MODE = 0

OPA_MODE = 0

HZ_MODE = 0

HZ_MODE = 0

HZ_MODE = 0

OTG Inactive

OTGIinactive

OTG Inactive

VBUS > UVLO

VBUS < VBUS(MIN)

VBUS < VBUS(MIN)

VBUS < UVLO

IN Condition

VBUS < VBUS(MIN)

or

or

CE = Low

CE = Low

CE = HIGH

No Faults

No Faults

OPA_MODE = 1

OPA_MODE = 1

OPA_MODE = 1

or HZ_MODE = 1

or HZ_MODE = 1

or HZ_MODE = 1

VBUS < VBUS(MIN)

VBUS < VBUS(MIN)

or

VBUS > UVLO

VBUS > VBUS(MIN)

OUT Condition

or

or

CE = HIGH

CE = HIGH

or VBUS > UVLO

or Faults

or Faults

OTG Active

or OTG Active

or OTG Active

Off

On

On

On

Buck

Off

Off

Off

On

Off

Off

On

Off

Boost

Off

Off

Off

Off

Q1

Off

On/Off

On

On

Note

POR when out

Copyright © 2008, Texas Instruments Incorporated

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Product Folder Link(s): bq24152