STPM098C datasheet(17/110 Pages) STMICROELECTRONICS

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3.1.3.1

VREF2 voltage monitor

VREF2 voltage level is monitored by means of dedicated UV and OV diagnosis. Hysteresis on thresholds and

filtering time are implemented.

If VREF2 ≤ VREF2_uv_th occurs for an interval longer than T_vref2_uv_flt, VREF2_UV flag is set and SAFE_HIZ

is established. The error flag remains set until the failure condition is removed and a rising edge on VR1_EN or

VR2_EN is detected. If analog input buffers are available, the failure condition can be removed by PMBus™

command CLEAR_FAULTS or by dedicated commands.

If VREF1 ≥ VREF2_ov_th occurs for an interval longer than T_vref2_ov_flt VREF2_OV flag is set and SAFE_HIZ

is established. The error flag remains set until the failure condition is removed and a rising edge on VR1_EN or

VR2_EN is detected. If analog input buffers are available, the failure condition can be removed by PMBUS

command CLEAR_FAULTS or by dedicated commands.

VREF2 monitor is safety relevant, then a self-check procedure is implemented.

Table 12. VREF2 monitor electrical characteristics

Symbol

Parameter

Test condition

Min Typ Max Unit

Notes

VREF2_uv_th

VREF2 undervoltage threshold

2.5 2.7

2.8

Comparator output low to

high

VREF2_uv_hys VREF2 undervoltage hysteresis

120

mV -

VREF2_ov_th

VREF2 overvoltage threshold

3.6 3.8

Comparator output low to

high

VREF2_ov_hys VREF2 overvoltage hysteresis

90 160 230

mV -

T_vref2_uv_flt

VREF2 undervoltage detection

filter time

CLK_SSM_EN = 0

μs

Digital filter

T_vref2_ov_flt

VREF2 overvoltage detection filter

time

CLK_SSM_EN = 0

μs

Digital filter

Figure 11. Power supply operative range

VREF2

VREF2_OV

(Internal signal)

VREF2_UV

(Internal signal)

VREF2_OV_TH

TVREF2_UV_flt

OPERATIVE

VREF2_UV_TH

VREF2_OV_HYS

VREF2_UV_HYS

TVREF2_UV_flt

TVREF2_OV_flt

Note:

1. VREF2 ≤ VREF2_uv_th (max) + VREF2_uv_hyst (max)

VREF2 is in undervoltage and SAFE_HIZ is established.

2. VREF2_uv_th ≤ VREF2 ≤ VREF2_ov_th

If no other LTC faults are detected the device mode depends on VR1_EN/VR2_EN status.

3. VREF2_ov_th ≤ VREF2

VREF2 is in overvoltage and SAFE_HIZ is established.

STPM098C

Functional description

DS14440 - Rev 1

page 17/110

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